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  73. Inheritance
  74. <h2>
  75. Inheritance
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  81. <h3><a href="index.html">Table of Contents</a></h3>
  82. <ul>
  83. <li><a class="reference internal" href="#">Inheritance</a><ul>
  84. <li><a class="reference internal" href="#nesting-blocks">Nesting Blocks</a></li>
  85. <li><a class="reference internal" href="#rendering-a-named-block-multiple-times">Rendering a Named Block Multiple Times</a></li>
  86. <li><a class="reference internal" href="#but-what-about-defs">But what about Defs?</a></li>
  87. <li><a class="reference internal" href="#using-the-next-namespace-to-produce-content-wrapping">Using the <tt class="docutils literal"><span class="pre">next</span></tt> Namespace to Produce Content Wrapping</a></li>
  88. <li><a class="reference internal" href="#using-the-parent-namespace-to-augment-defs">Using the <tt class="docutils literal"><span class="pre">parent</span></tt> Namespace to Augment Defs</a></li>
  89. <li><a class="reference internal" href="#inheritable-attributes">Inheritable Attributes</a></li>
  90. </ul>
  91. </li>
  92. </ul>
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  111. <div class="section" id="inheritance">
  112. <span id="inheritance-toplevel"></span><h1>Inheritance<a class="headerlink" href="#inheritance" title="Permalink to this headline">¶</a></h1>
  113. <div class="admonition note">
  114. <p class="first admonition-title">Note</p>
  115. <p class="last">Most of the inheritance examples here take advantage of a feature that&#8217;s
  116. new in Mako as of version 0.4.1 called the &#8220;block&#8221;. This tag is very similar to
  117. the &#8220;def&#8221; tag but is more streamlined for usage with inheritance. Note that
  118. all of the examples here which use blocks can also use defs instead. Contrasting
  119. usages will be illustrated.</p>
  120. </div>
  121. <p>Using template inheritance, two or more templates can organize
  122. themselves into an <strong>inheritance chain</strong>, where content and
  123. functions from all involved templates can be intermixed. The
  124. general paradigm of template inheritance is this: if a template
  125. <tt class="docutils literal"><span class="pre">A</span></tt> inherits from template <tt class="docutils literal"><span class="pre">B</span></tt>, then template <tt class="docutils literal"><span class="pre">A</span></tt> agrees
  126. to send the executional control to template <tt class="docutils literal"><span class="pre">B</span></tt> at runtime
  127. (<tt class="docutils literal"><span class="pre">A</span></tt> is called the <strong>inheriting</strong> template). Template <tt class="docutils literal"><span class="pre">B</span></tt>,
  128. the <strong>inherited</strong> template, then makes decisions as to what
  129. resources from <tt class="docutils literal"><span class="pre">A</span></tt> shall be executed.</p>
  130. <p>In practice, it looks like this. Here&#8217;s a hypothetical inheriting
  131. template, <tt class="docutils literal"><span class="pre">index.html</span></tt>:</p>
  132. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## index.html</span><span class="x"></span>
  133. <span class="cp">&lt;%</span><span class="nb">inherit</span> <span class="na">file=</span><span class="s">&quot;base.html&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  134. <span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;header&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  135. <span class="x"> this is some header content</span>
  136. <span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  137. <span class="x">this is the body content.</span>
  138. </pre></div>
  139. </div>
  140. <p>And <tt class="docutils literal"><span class="pre">base.html</span></tt>, the inherited template:</p>
  141. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## base.html</span><span class="x"></span>
  142. <span class="x">&lt;html&gt;</span>
  143. <span class="x"> &lt;body&gt;</span>
  144. <span class="x"> &lt;div class=&quot;header&quot;&gt;</span>
  145. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;header&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  146. <span class="x"> &lt;/div&gt;</span>
  147. <span class="x"> </span><span class="cp">${</span><span class="bp">self</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  148. <span class="x"> &lt;div class=&quot;footer&quot;&gt;</span>
  149. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;footer&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  150. <span class="x"> this is the footer</span>
  151. <span class="x"> </span><span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  152. <span class="x"> &lt;/div&gt;</span>
  153. <span class="x"> &lt;/body&gt;</span>
  154. <span class="x">&lt;/html&gt;</span>
  155. </pre></div>
  156. </div>
  157. <p>Here is a breakdown of the execution:</p>
  158. <ol class="arabic">
  159. <li><p class="first">When <tt class="docutils literal"><span class="pre">index.html</span></tt> is rendered, control immediately passes to
  160. <tt class="docutils literal"><span class="pre">base.html</span></tt>.</p>
  161. </li>
  162. <li><p class="first"><tt class="docutils literal"><span class="pre">base.html</span></tt> then renders the top part of an HTML document,
  163. then invokes the <tt class="docutils literal"><span class="pre">&lt;%block</span> <span class="pre">name=&quot;header&quot;&gt;</span></tt> block. It invokes the
  164. underlying <tt class="docutils literal"><span class="pre">header()</span></tt> function off of a built-in namespace
  165. called <tt class="docutils literal"><span class="pre">self</span></tt> (this namespace was first introduced in the
  166. <a class="reference internal" href="namespaces.html"><em>Namespaces chapter</em></a> in <a class="reference internal" href="namespaces.html#namespace-self"><em>self</em></a>). Since
  167. <tt class="docutils literal"><span class="pre">index.html</span></tt> is the topmost template and also defines a block
  168. called <tt class="docutils literal"><span class="pre">header</span></tt>, it&#8217;s this <tt class="docutils literal"><span class="pre">header</span></tt> block that ultimately gets
  169. executed &#8211; instead of the one that&#8217;s present in <tt class="docutils literal"><span class="pre">base.html</span></tt>.</p>
  170. </li>
  171. <li><p class="first">Control comes back to <tt class="docutils literal"><span class="pre">base.html</span></tt>. Some more HTML is
  172. rendered.</p>
  173. </li>
  174. <li><p class="first"><tt class="docutils literal"><span class="pre">base.html</span></tt> executes <tt class="docutils literal"><span class="pre">self.body()</span></tt>. The <tt class="docutils literal"><span class="pre">body()</span></tt>
  175. function on all template-based namespaces refers to the main
  176. body of the template, therefore the main body of
  177. <tt class="docutils literal"><span class="pre">index.html</span></tt> is rendered.</p>
  178. </li>
  179. <li><p class="first">When <tt class="docutils literal"><span class="pre">&lt;%block</span> <span class="pre">name=&quot;header&quot;&gt;</span></tt> is encountered in <tt class="docutils literal"><span class="pre">index.html</span></tt>
  180. during the <tt class="docutils literal"><span class="pre">self.body()</span></tt> call, a conditional is checked &#8211; does the
  181. current inherited template, i.e. <tt class="docutils literal"><span class="pre">base.html</span></tt>, also define this block? If yes,
  182. the <tt class="docutils literal"><span class="pre">&lt;%block&gt;</span></tt> is <strong>not</strong> executed here &#8211; the inheritance
  183. mechanism knows that the parent template is responsible for rendering
  184. this block (and in fact it already has). In other words a block
  185. only renders in its <em>basemost scope</em>.</p>
  186. </li>
  187. <li><p class="first">Control comes back to <tt class="docutils literal"><span class="pre">base.html</span></tt>. More HTML is rendered,
  188. then the <tt class="docutils literal"><span class="pre">&lt;%block</span> <span class="pre">name=&quot;footer&quot;&gt;</span></tt> expression is invoked.</p>
  189. </li>
  190. <li><p class="first">The <tt class="docutils literal"><span class="pre">footer</span></tt> block is only defined in <tt class="docutils literal"><span class="pre">base.html</span></tt>, so being
  191. the topmost definition of <tt class="docutils literal"><span class="pre">footer</span></tt>, it&#8217;s the one that
  192. executes. If <tt class="docutils literal"><span class="pre">index.html</span></tt> also specified <tt class="docutils literal"><span class="pre">footer</span></tt>, then
  193. its version would <strong>override</strong> that of the base.</p>
  194. </li>
  195. <li><p class="first"><tt class="docutils literal"><span class="pre">base.html</span></tt> finishes up rendering its HTML and the template
  196. is complete, producing:</p>
  197. <div class="highlight-html"><div class="highlight"><pre><span class="nt">&lt;html&gt;</span>
  198. <span class="nt">&lt;body&gt;</span>
  199. <span class="nt">&lt;div</span> <span class="na">class=</span><span class="s">&quot;header&quot;</span><span class="nt">&gt;</span>
  200. this is some header content
  201. <span class="nt">&lt;/div&gt;</span>
  202. this is the body content.
  203. <span class="nt">&lt;div</span> <span class="na">class=</span><span class="s">&quot;footer&quot;</span><span class="nt">&gt;</span>
  204. this is the footer
  205. <span class="nt">&lt;/div&gt;</span>
  206. <span class="nt">&lt;/body&gt;</span>
  207. <span class="nt">&lt;/html&gt;</span>
  208. </pre></div>
  209. </div>
  210. </li>
  211. </ol>
  212. <p>...and that is template inheritance in a nutshell. The main idea
  213. is that the methods that you call upon <tt class="docutils literal"><span class="pre">self</span></tt> always
  214. correspond to the topmost definition of that method. Very much
  215. the way <tt class="docutils literal"><span class="pre">self</span></tt> works in a Python class, even though Mako is
  216. not actually using Python class inheritance to implement this
  217. functionality. (Mako doesn&#8217;t take the &#8220;inheritance&#8221; metaphor too
  218. seriously; while useful to setup some commonly recognized
  219. semantics, a textual template is not very much like an
  220. object-oriented class construct in practice).</p>
  221. <div class="section" id="nesting-blocks">
  222. <h2>Nesting Blocks<a class="headerlink" href="#nesting-blocks" title="Permalink to this headline">¶</a></h2>
  223. <p>The named blocks defined in an inherited template can also be nested within
  224. other blocks. The name given to each block is globally accessible via any inheriting
  225. template. We can add a new block <tt class="docutils literal"><span class="pre">title</span></tt> to our <tt class="docutils literal"><span class="pre">header</span></tt> block:</p>
  226. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## base.html</span><span class="x"></span>
  227. <span class="x">&lt;html&gt;</span>
  228. <span class="x"> &lt;body&gt;</span>
  229. <span class="x"> &lt;div class=&quot;header&quot;&gt;</span>
  230. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;header&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  231. <span class="x"> &lt;h2&gt;</span>
  232. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;title&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  233. <span class="x"> &lt;/h2&gt;</span>
  234. <span class="x"> </span><span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  235. <span class="x"> &lt;/div&gt;</span>
  236. <span class="x"> </span><span class="cp">${</span><span class="bp">self</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  237. <span class="x"> &lt;div class=&quot;footer&quot;&gt;</span>
  238. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;footer&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  239. <span class="x"> this is the footer</span>
  240. <span class="x"> </span><span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  241. <span class="x"> &lt;/div&gt;</span>
  242. <span class="x"> &lt;/body&gt;</span>
  243. <span class="x">&lt;/html&gt;</span>
  244. </pre></div>
  245. </div>
  246. <p>The inheriting template can name either or both of <tt class="docutils literal"><span class="pre">header</span></tt> and <tt class="docutils literal"><span class="pre">title</span></tt>, separately
  247. or nested themselves:</p>
  248. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## index.html</span><span class="x"></span>
  249. <span class="cp">&lt;%</span><span class="nb">inherit</span> <span class="na">file=</span><span class="s">&quot;base.html&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  250. <span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;header&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  251. <span class="x"> this is some header content</span>
  252. <span class="x"> </span><span class="cp">${</span><span class="n">parent</span><span class="o">.</span><span class="n">header</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  253. <span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  254. <span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;title&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  255. <span class="x"> this is the title</span>
  256. <span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  257. <span class="x">this is the body content.</span>
  258. </pre></div>
  259. </div>
  260. <p>Note when we overrode <tt class="docutils literal"><span class="pre">header</span></tt>, we added an extra call <tt class="docutils literal"><span class="pre">${parent.header()}</span></tt> in order to invoke
  261. the parent&#8217;s <tt class="docutils literal"><span class="pre">header</span></tt> block in addition to our own. That&#8217;s described in more detail below,
  262. in <a class="reference internal" href="#parent-namespace"><em>Using the parent Namespace to Augment Defs</em></a>.</p>
  263. </div>
  264. <div class="section" id="rendering-a-named-block-multiple-times">
  265. <h2>Rendering a Named Block Multiple Times<a class="headerlink" href="#rendering-a-named-block-multiple-times" title="Permalink to this headline">¶</a></h2>
  266. <p>Recall from the section <a class="reference internal" href="defs.html#blocks"><em>Using Blocks</em></a> that a named block is just like a <tt class="docutils literal"><span class="pre">&lt;%def&gt;</span></tt>,
  267. with some different usage rules. We can call one of our named sections distinctly, for example
  268. a section that is used more than once, such as the title of a page:</p>
  269. <div class="highlight-mako"><div class="highlight"><pre><span class="x">&lt;html&gt;</span>
  270. <span class="x"> &lt;head&gt;</span>
  271. <span class="x"> &lt;title&gt;</span><span class="cp">${</span><span class="bp">self</span><span class="o">.</span><span class="n">title</span><span class="p">()</span><span class="cp">}</span><span class="x">&lt;/title&gt;</span>
  272. <span class="x"> &lt;/head&gt;</span>
  273. <span class="x"> &lt;body&gt;</span>
  274. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;header&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  275. <span class="x"> &lt;h2&gt;</span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;title&quot;</span><span class="cp">/&gt;</span><span class="x">&lt;/h2&gt;</span>
  276. <span class="x"> </span><span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  277. <span class="x"> </span><span class="cp">${</span><span class="bp">self</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  278. <span class="x"> &lt;/body&gt;</span>
  279. <span class="x">&lt;/html&gt;</span>
  280. </pre></div>
  281. </div>
  282. <p>Where above an inheriting template can define <tt class="docutils literal"><span class="pre">&lt;%block</span> <span class="pre">name=&quot;title&quot;&gt;</span></tt> just once, and it will be
  283. used in the base template both in the <tt class="docutils literal"><span class="pre">&lt;title&gt;</span></tt> section as well as the <tt class="docutils literal"><span class="pre">&lt;h2&gt;</span></tt>.</p>
  284. </div>
  285. <div class="section" id="but-what-about-defs">
  286. <h2>But what about Defs?<a class="headerlink" href="#but-what-about-defs" title="Permalink to this headline">¶</a></h2>
  287. <p>The previous example used the <tt class="docutils literal"><span class="pre">&lt;%block&gt;</span></tt> tag to produce areas of content
  288. to be overridden. Before Mako 0.4.1, there wasn&#8217;t any such tag &#8211; instead
  289. there was only the <tt class="docutils literal"><span class="pre">&lt;%def&gt;</span></tt> tag. As it turns out, named blocks and defs are
  290. largely interchangeable. The def simply doesn&#8217;t call itself automatically,
  291. and has more open-ended naming and scoping rules that are more flexible and similar
  292. to Python itself, but less suited towards layout. The first example from
  293. this chapter using defs would look like:</p>
  294. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## index.html</span><span class="x"></span>
  295. <span class="cp">&lt;%</span><span class="nb">inherit</span> <span class="na">file=</span><span class="s">&quot;base.html&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  296. <span class="cp">&lt;%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">&quot;header()&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  297. <span class="x"> this is some header content</span>
  298. <span class="cp">&lt;/%</span><span class="nb">def</span><span class="cp">&gt;</span><span class="x"></span>
  299. <span class="x">this is the body content.</span>
  300. </pre></div>
  301. </div>
  302. <p>And <tt class="docutils literal"><span class="pre">base.html</span></tt>, the inherited template:</p>
  303. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## base.html</span><span class="x"></span>
  304. <span class="x">&lt;html&gt;</span>
  305. <span class="x"> &lt;body&gt;</span>
  306. <span class="x"> &lt;div class=&quot;header&quot;&gt;</span>
  307. <span class="x"> </span><span class="cp">${</span><span class="bp">self</span><span class="o">.</span><span class="n">header</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  308. <span class="x"> &lt;/div&gt;</span>
  309. <span class="x"> </span><span class="cp">${</span><span class="bp">self</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  310. <span class="x"> &lt;div class=&quot;footer&quot;&gt;</span>
  311. <span class="x"> </span><span class="cp">${</span><span class="bp">self</span><span class="o">.</span><span class="n">footer</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  312. <span class="x"> &lt;/div&gt;</span>
  313. <span class="x"> &lt;/body&gt;</span>
  314. <span class="x">&lt;/html&gt;</span>
  315. <span class="cp">&lt;%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">&quot;header()&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  316. <span class="cp">&lt;%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">&quot;footer()&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  317. <span class="x"> this is the footer</span>
  318. <span class="cp">&lt;/%</span><span class="nb">def</span><span class="cp">&gt;</span><span class="x"></span>
  319. </pre></div>
  320. </div>
  321. <p>Above, we illustrate that defs differ from blocks in that their definition
  322. and invocation are defined in two separate places, instead of at once. You can <em>almost</em> do exactly what a
  323. block does if you put the two together:</p>
  324. <div class="highlight-mako"><div class="highlight"><pre><span class="x">&lt;div class=&quot;header&quot;&gt;</span>
  325. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">&quot;header()&quot;</span><span class="cp">&gt;&lt;/%</span><span class="nb">def</span><span class="cp">&gt;${</span><span class="bp">self</span><span class="o">.</span><span class="n">header</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  326. <span class="x">&lt;/div&gt;</span>
  327. </pre></div>
  328. </div>
  329. <p>The <tt class="docutils literal"><span class="pre">&lt;%block&gt;</span></tt> is obviously more streamlined than the <tt class="docutils literal"><span class="pre">&lt;%def&gt;</span></tt> for this kind
  330. of usage. In addition,
  331. the above &#8220;inline&#8221; approach with <tt class="docutils literal"><span class="pre">&lt;%def&gt;</span></tt> does not work with nesting:</p>
  332. <div class="highlight-mako"><div class="highlight"><pre><span class="x">&lt;head&gt;</span>
  333. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">&quot;header()&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  334. <span class="x"> &lt;title&gt;</span>
  335. <span class="x"> ## this won&#39;t work !</span>
  336. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">&quot;title()&quot;</span><span class="cp">&gt;</span><span class="x">default title</span><span class="cp">&lt;/%</span><span class="nb">def</span><span class="cp">&gt;${</span><span class="bp">self</span><span class="o">.</span><span class="n">title</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  337. <span class="x"> &lt;/title&gt;</span>
  338. <span class="x"> </span><span class="cp">&lt;/%</span><span class="nb">def</span><span class="cp">&gt;${</span><span class="bp">self</span><span class="o">.</span><span class="n">header</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  339. <span class="x">&lt;/head&gt;</span>
  340. </pre></div>
  341. </div>
  342. <p>Where above, the <tt class="docutils literal"><span class="pre">title()</span></tt> def, because it&#8217;s a def within a def, is not part of the
  343. template&#8217;s exported namespace and will not be part of <tt class="docutils literal"><span class="pre">self</span></tt>. If the inherited template
  344. did define its own <tt class="docutils literal"><span class="pre">title</span></tt> def at the top level, it would be called, but the &#8220;default title&#8221;
  345. above is not present at all on <tt class="docutils literal"><span class="pre">self</span></tt> no matter what. For this to work as expected
  346. you&#8217;d instead need to say:</p>
  347. <div class="highlight-mako"><div class="highlight"><pre><span class="x">&lt;head&gt;</span>
  348. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">&quot;header()&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  349. <span class="x"> &lt;title&gt;</span>
  350. <span class="x"> </span><span class="cp">${</span><span class="bp">self</span><span class="o">.</span><span class="n">title</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  351. <span class="x"> &lt;/title&gt;</span>
  352. <span class="x"> </span><span class="cp">&lt;/%</span><span class="nb">def</span><span class="cp">&gt;${</span><span class="bp">self</span><span class="o">.</span><span class="n">header</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  353. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">def</span> <span class="na">name=</span><span class="s">&quot;title()&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  354. <span class="x">&lt;/head&gt;</span>
  355. </pre></div>
  356. </div>
  357. <p>That is, <tt class="docutils literal"><span class="pre">title</span></tt> is defined outside of any other defs so that it is in the <tt class="docutils literal"><span class="pre">self</span></tt> namespace.
  358. It works, but the definition needs to be potentially far away from the point of render.</p>
  359. <p>A named block is always placed in the <tt class="docutils literal"><span class="pre">self</span></tt> namespace, regardless of nesting,
  360. so this restriction is lifted:</p>
  361. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## base.html</span><span class="x"></span>
  362. <span class="x">&lt;head&gt;</span>
  363. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;header&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  364. <span class="x"> &lt;title&gt;</span>
  365. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;title&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  366. <span class="x"> &lt;/title&gt;</span>
  367. <span class="x"> </span><span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  368. <span class="x">&lt;/head&gt;</span>
  369. </pre></div>
  370. </div>
  371. <p>The above template defines <tt class="docutils literal"><span class="pre">title</span></tt> inside of <tt class="docutils literal"><span class="pre">header</span></tt>, and an inheriting template can define
  372. one or both in <strong>any</strong> configuration, nested inside each other or not, in order for them to be used:</p>
  373. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## index.html</span><span class="x"></span>
  374. <span class="cp">&lt;%</span><span class="nb">inherit</span> <span class="na">file=</span><span class="s">&quot;base.html&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  375. <span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;title&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  376. <span class="x"> the title</span>
  377. <span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  378. <span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;header&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  379. <span class="x"> the header</span>
  380. <span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  381. </pre></div>
  382. </div>
  383. <p>So while the <tt class="docutils literal"><span class="pre">&lt;%block&gt;</span></tt> tag lifts the restriction of nested blocks not being available externally,
  384. in order to achieve this it <em>adds</em> the restriction that all block names in a single template need
  385. to be globally unique within the template, and additionally that a <tt class="docutils literal"><span class="pre">&lt;%block&gt;</span></tt> can&#8217;t be defined
  386. inside of a <tt class="docutils literal"><span class="pre">&lt;%def&gt;</span></tt>. It&#8217;s a more restricted tag suited towards a more specific use case than <tt class="docutils literal"><span class="pre">&lt;%def&gt;</span></tt>.</p>
  387. </div>
  388. <div class="section" id="using-the-next-namespace-to-produce-content-wrapping">
  389. <h2>Using the <tt class="docutils literal"><span class="pre">next</span></tt> Namespace to Produce Content Wrapping<a class="headerlink" href="#using-the-next-namespace-to-produce-content-wrapping" title="Permalink to this headline">¶</a></h2>
  390. <p>Sometimes you have an inheritance chain that spans more than two
  391. templates. Or maybe you don&#8217;t, but you&#8217;d like to build your
  392. system such that extra inherited templates can be inserted in
  393. the middle of a chain where they would be smoothly integrated.
  394. If each template wants to define its layout just within its main
  395. body, you can&#8217;t just call <tt class="docutils literal"><span class="pre">self.body()</span></tt> to get at the
  396. inheriting template&#8217;s body, since that is only the topmost body.
  397. To get at the body of the <em>next</em> template, you call upon the
  398. namespace <tt class="docutils literal"><span class="pre">next</span></tt>, which is the namespace of the template
  399. <strong>immediately following</strong> the current template.</p>
  400. <p>Lets change the line in <tt class="docutils literal"><span class="pre">base.html</span></tt> which calls upon
  401. <tt class="docutils literal"><span class="pre">self.body()</span></tt> to instead call upon <tt class="docutils literal"><span class="pre">next.body()</span></tt>:</p>
  402. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## base.html</span><span class="x"></span>
  403. <span class="x">&lt;html&gt;</span>
  404. <span class="x"> &lt;body&gt;</span>
  405. <span class="x"> &lt;div class=&quot;header&quot;&gt;</span>
  406. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;header&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  407. <span class="x"> &lt;/div&gt;</span>
  408. <span class="x"> </span><span class="cp">${</span><span class="nb">next</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  409. <span class="x"> &lt;div class=&quot;footer&quot;&gt;</span>
  410. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;footer&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  411. <span class="x"> this is the footer</span>
  412. <span class="x"> </span><span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  413. <span class="x"> &lt;/div&gt;</span>
  414. <span class="x"> &lt;/body&gt;</span>
  415. <span class="x">&lt;/html&gt;</span>
  416. </pre></div>
  417. </div>
  418. <p>Lets also add an intermediate template called <tt class="docutils literal"><span class="pre">layout.html</span></tt>,
  419. which inherits from <tt class="docutils literal"><span class="pre">base.html</span></tt>:</p>
  420. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## layout.html</span><span class="x"></span>
  421. <span class="cp">&lt;%</span><span class="nb">inherit</span> <span class="na">file=</span><span class="s">&quot;base.html&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  422. <span class="x">&lt;ul&gt;</span>
  423. <span class="x"> </span><span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;toolbar&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  424. <span class="x"> &lt;li&gt;selection 1&lt;/li&gt;</span>
  425. <span class="x"> &lt;li&gt;selection 2&lt;/li&gt;</span>
  426. <span class="x"> &lt;li&gt;selection 3&lt;/li&gt;</span>
  427. <span class="x"> </span><span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  428. <span class="x">&lt;/ul&gt;</span>
  429. <span class="x">&lt;div class=&quot;mainlayout&quot;&gt;</span>
  430. <span class="x"> </span><span class="cp">${</span><span class="nb">next</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  431. <span class="x">&lt;/div&gt;</span>
  432. </pre></div>
  433. </div>
  434. <p>And finally change <tt class="docutils literal"><span class="pre">index.html</span></tt> to inherit from
  435. <tt class="docutils literal"><span class="pre">layout.html</span></tt> instead:</p>
  436. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## index.html</span><span class="x"></span>
  437. <span class="cp">&lt;%</span><span class="nb">inherit</span> <span class="na">file=</span><span class="s">&quot;layout.html&quot;</span><span class="cp">/&gt;</span>
  438. <span class="cp">## .. rest of template</span><span class="x"></span>
  439. </pre></div>
  440. </div>
  441. <p>In this setup, each call to <tt class="docutils literal"><span class="pre">next.body()</span></tt> will render the body
  442. of the next template in the inheritance chain (which can be
  443. written as <tt class="docutils literal"><span class="pre">base.html</span> <span class="pre">-&gt;</span> <span class="pre">layout.html</span> <span class="pre">-&gt;</span> <span class="pre">index.html</span></tt>). Control
  444. is still first passed to the bottommost template <tt class="docutils literal"><span class="pre">base.html</span></tt>,
  445. and <tt class="docutils literal"><span class="pre">self</span></tt> still references the topmost definition of any
  446. particular def.</p>
  447. <p>The output we get would be:</p>
  448. <div class="highlight-html"><div class="highlight"><pre><span class="nt">&lt;html&gt;</span>
  449. <span class="nt">&lt;body&gt;</span>
  450. <span class="nt">&lt;div</span> <span class="na">class=</span><span class="s">&quot;header&quot;</span><span class="nt">&gt;</span>
  451. this is some header content
  452. <span class="nt">&lt;/div&gt;</span>
  453. <span class="nt">&lt;ul&gt;</span>
  454. <span class="nt">&lt;li&gt;</span>selection 1<span class="nt">&lt;/li&gt;</span>
  455. <span class="nt">&lt;li&gt;</span>selection 2<span class="nt">&lt;/li&gt;</span>
  456. <span class="nt">&lt;li&gt;</span>selection 3<span class="nt">&lt;/li&gt;</span>
  457. <span class="nt">&lt;/ul&gt;</span>
  458. <span class="nt">&lt;div</span> <span class="na">class=</span><span class="s">&quot;mainlayout&quot;</span><span class="nt">&gt;</span>
  459. this is the body content.
  460. <span class="nt">&lt;/div&gt;</span>
  461. <span class="nt">&lt;div</span> <span class="na">class=</span><span class="s">&quot;footer&quot;</span><span class="nt">&gt;</span>
  462. this is the footer
  463. <span class="nt">&lt;/div&gt;</span>
  464. <span class="nt">&lt;/body&gt;</span>
  465. <span class="nt">&lt;/html&gt;</span>
  466. </pre></div>
  467. </div>
  468. <p>So above, we have the <tt class="docutils literal"><span class="pre">&lt;html&gt;</span></tt>, <tt class="docutils literal"><span class="pre">&lt;body&gt;</span></tt> and
  469. <tt class="docutils literal"><span class="pre">header</span></tt>/<tt class="docutils literal"><span class="pre">footer</span></tt> layout of <tt class="docutils literal"><span class="pre">base.html</span></tt>, we have the
  470. <tt class="docutils literal"><span class="pre">&lt;ul&gt;</span></tt> and <tt class="docutils literal"><span class="pre">mainlayout</span></tt> section of <tt class="docutils literal"><span class="pre">layout.html</span></tt>, and the
  471. main body of <tt class="docutils literal"><span class="pre">index.html</span></tt> as well as its overridden <tt class="docutils literal"><span class="pre">header</span></tt>
  472. def. The <tt class="docutils literal"><span class="pre">layout.html</span></tt> template is inserted into the middle of
  473. the chain without <tt class="docutils literal"><span class="pre">base.html</span></tt> having to change anything.
  474. Without the <tt class="docutils literal"><span class="pre">next</span></tt> namespace, only the main body of
  475. <tt class="docutils literal"><span class="pre">index.html</span></tt> could be used; there would be no way to call
  476. <tt class="docutils literal"><span class="pre">layout.html</span></tt>&#8216;s body content.</p>
  477. </div>
  478. <div class="section" id="using-the-parent-namespace-to-augment-defs">
  479. <span id="parent-namespace"></span><h2>Using the <tt class="docutils literal"><span class="pre">parent</span></tt> Namespace to Augment Defs<a class="headerlink" href="#using-the-parent-namespace-to-augment-defs" title="Permalink to this headline">¶</a></h2>
  480. <p>Lets now look at the other inheritance-specific namespace, the
  481. opposite of <tt class="docutils literal"><span class="pre">next</span></tt> called <tt class="docutils literal"><span class="pre">parent</span></tt>. <tt class="docutils literal"><span class="pre">parent</span></tt> is the
  482. namespace of the template <strong>immediately preceding</strong> the current
  483. template. What&#8217;s useful about this namespace is that
  484. defs or blocks can call upon their overridden versions.
  485. This is not as hard as it sounds and
  486. is very much like using the <tt class="docutils literal"><span class="pre">super</span></tt> keyword in Python. Lets
  487. modify <tt class="docutils literal"><span class="pre">index.html</span></tt> to augment the list of selections provided
  488. by the <tt class="docutils literal"><span class="pre">toolbar</span></tt> function in <tt class="docutils literal"><span class="pre">layout.html</span></tt>:</p>
  489. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">## index.html</span><span class="x"></span>
  490. <span class="cp">&lt;%</span><span class="nb">inherit</span> <span class="na">file=</span><span class="s">&quot;layout.html&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  491. <span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;header&quot;</span><span class="cp">&gt;</span><span class="x"></span>
  492. <span class="x"> this is some header content</span>
  493. <span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  494. <span class="cp">&lt;%</span><span class="nb">block</span> <span class="na">name=</span><span class="s">&quot;toolbar&quot;</span><span class="cp">&gt;</span>
  495. <span class="cp">## call the parent&#39;s toolbar first</span><span class="x"></span>
  496. <span class="x"> </span><span class="cp">${</span><span class="n">parent</span><span class="o">.</span><span class="n">toolbar</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  497. <span class="x"> &lt;li&gt;selection 4&lt;/li&gt;</span>
  498. <span class="x"> &lt;li&gt;selection 5&lt;/li&gt;</span>
  499. <span class="cp">&lt;/%</span><span class="nb">block</span><span class="cp">&gt;</span><span class="x"></span>
  500. <span class="x">this is the body content.</span>
  501. </pre></div>
  502. </div>
  503. <p>Above, we implemented a <tt class="docutils literal"><span class="pre">toolbar()</span></tt> function, which is meant
  504. to override the definition of <tt class="docutils literal"><span class="pre">toolbar</span></tt> within the inherited
  505. template <tt class="docutils literal"><span class="pre">layout.html</span></tt>. However, since we want the content
  506. from that of <tt class="docutils literal"><span class="pre">layout.html</span></tt> as well, we call it via the
  507. <tt class="docutils literal"><span class="pre">parent</span></tt> namespace whenever we want it&#8217;s content, in this case
  508. before we add our own selections. So the output for the whole
  509. thing is now:</p>
  510. <div class="highlight-html"><div class="highlight"><pre><span class="nt">&lt;html&gt;</span>
  511. <span class="nt">&lt;body&gt;</span>
  512. <span class="nt">&lt;div</span> <span class="na">class=</span><span class="s">&quot;header&quot;</span><span class="nt">&gt;</span>
  513. this is some header content
  514. <span class="nt">&lt;/div&gt;</span>
  515. <span class="nt">&lt;ul&gt;</span>
  516. <span class="nt">&lt;li&gt;</span>selection 1<span class="nt">&lt;/li&gt;</span>
  517. <span class="nt">&lt;li&gt;</span>selection 2<span class="nt">&lt;/li&gt;</span>
  518. <span class="nt">&lt;li&gt;</span>selection 3<span class="nt">&lt;/li&gt;</span>
  519. <span class="nt">&lt;li&gt;</span>selection 4<span class="nt">&lt;/li&gt;</span>
  520. <span class="nt">&lt;li&gt;</span>selection 5<span class="nt">&lt;/li&gt;</span>
  521. <span class="nt">&lt;/ul&gt;</span>
  522. <span class="nt">&lt;div</span> <span class="na">class=</span><span class="s">&quot;mainlayout&quot;</span><span class="nt">&gt;</span>
  523. this is the body content.
  524. <span class="nt">&lt;/div&gt;</span>
  525. <span class="nt">&lt;div</span> <span class="na">class=</span><span class="s">&quot;footer&quot;</span><span class="nt">&gt;</span>
  526. this is the footer
  527. <span class="nt">&lt;/div&gt;</span>
  528. <span class="nt">&lt;/body&gt;</span>
  529. <span class="nt">&lt;/html&gt;</span>
  530. </pre></div>
  531. </div>
  532. <p>and you&#8217;re now a template inheritance ninja!</p>
  533. </div>
  534. <div class="section" id="inheritable-attributes">
  535. <h2>Inheritable Attributes<a class="headerlink" href="#inheritable-attributes" title="Permalink to this headline">¶</a></h2>
  536. <p>The <a class="reference internal" href="namespaces.html#mako.runtime.Namespace.attr" title="mako.runtime.Namespace.attr"><tt class="xref py py-attr docutils literal"><span class="pre">attr</span></tt></a> accessor of the <a class="reference internal" href="namespaces.html#mako.runtime.Namespace" title="mako.runtime.Namespace"><tt class="xref py py-class docutils literal"><span class="pre">Namespace</span></tt></a> object
  537. allows access to module level variables declared in a template. By accessing
  538. <tt class="docutils literal"><span class="pre">self.attr</span></tt>, you can access regular attributes from the
  539. inheritance chain as declared in <tt class="docutils literal"><span class="pre">&lt;%!</span> <span class="pre">%&gt;</span></tt> sections. Such as:</p>
  540. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">&lt;%!</span>
  541. <span class="n">class_</span> <span class="o">=</span> <span class="s">&quot;grey&quot;</span>
  542. <span class="cp">%&gt;</span><span class="x"></span>
  543. <span class="x">&lt;div class=&quot;</span><span class="cp">${</span><span class="bp">self</span><span class="o">.</span><span class="n">attr</span><span class="o">.</span><span class="n">class_</span><span class="cp">}</span><span class="x">&quot;&gt;</span>
  544. <span class="x"> </span><span class="cp">${</span><span class="bp">self</span><span class="o">.</span><span class="n">body</span><span class="p">()</span><span class="cp">}</span><span class="x"></span>
  545. <span class="x">&lt;/div&gt;</span>
  546. </pre></div>
  547. </div>
  548. <p>If an inheriting template overrides <tt class="docutils literal"><span class="pre">class_</span></tt> to be
  549. <tt class="docutils literal"><span class="pre">&quot;white&quot;</span></tt>, as in:</p>
  550. <div class="highlight-mako"><div class="highlight"><pre><span class="cp">&lt;%!</span>
  551. <span class="n">class_</span> <span class="o">=</span> <span class="s">&quot;white&quot;</span>
  552. <span class="cp">%&gt;</span><span class="x"></span>
  553. <span class="cp">&lt;%</span><span class="nb">inherit</span> <span class="na">file=</span><span class="s">&quot;parent.html&quot;</span><span class="cp">/&gt;</span><span class="x"></span>
  554. <span class="x">This is the body</span>
  555. </pre></div>
  556. </div>
  557. <p>you&#8217;ll get output like:</p>
  558. <div class="highlight-html"><div class="highlight"><pre><span class="nt">&lt;div</span> <span class="na">class=</span><span class="s">&quot;white&quot;</span><span class="nt">&gt;</span>
  559. This is the body
  560. <span class="nt">&lt;/div&gt;</span>
  561. </pre></div>
  562. </div>
  563. </div>
  564. </div>
  565. </div>
  566. </div>
  567. <div id="docs-bottom-navigation" class="docs-navigation-links">
  568. Previous:
  569. <a href="namespaces.html" title="previous chapter">Namespaces</a>
  570. Next:
  571. <a href="filtering.html" title="next chapter">Filtering and Buffering</a>
  572. <div id="docs-copyright">
  573. &copy; Copyright the Mako authors and contributors.
  574. Documentation generated using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3
  575. with Mako templates.
  576. </div>
  577. </div>
  578. </div>
  579. <div class="clearfix">
  580. <hr/>
  581. <div class="copyright">Website content copyright &copy; by Michael Bayer.
  582. All rights reserved. Mako and its documentation are licensed
  583. under the MIT license. mike(&)zzzcomputing.com</div>
  584. </div>
  585. </div>
  586. </body>
  587. </html>