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| <h1 class="content-header header-section1" id="dgui_misc_var" itemprop="headline">Defining variables in the template</h1> |
| </div></div><p>As we have described, a template can use the variables defined |
| in the data-model. A template can also define variables outside the |
| data-model for its own use. These temporary variables can be created |
| and replaced using FTL directives. Note that each <a href="gloss.html#gloss.templateProcessingJob">template processing job</a> |
| has its own private set of these variables that exists while the given |
| page is being rendered. This variable set is initially empty, and will |
| be thrown away when the template processing job has been |
| finished.</p><p>You access a variable that you have defined in the template |
| exactly as if it were a variable in the data-model root. The variable |
| has precedence over any variable of the same name defined in the |
| data-model. That is, if you define a variable called ``foo'' and |
| coincidentally, there is a ``foo'' in the data-model as well, then the |
| variable created in the template will hide (not overwrite!) the |
| variable in the data-model root. For example, |
| <code class="inline-code">${foo}</code> will print the value of the variable created |
| in the template.</p><p>There are 3 kind of variables that are defined in a |
| template:</p><ul> |
| <li> |
| <p><strong>``plain'' variables</strong>: They |
| are accessible from everywhere in the template, or from the |
| templates inserted with <code class="inline-code">include</code> directive. You |
| can create and replace these variables with the <a href="ref_directive_assign.html#ref.directive.assign"><code>assign</code></a> or |
| <a href="ref_directive_macro.html#ref.directive.macro"><code>macro</code> |
| directives</a>.</p> |
| </li> |
| |
| <li> |
| <p><strong>Local variables</strong>: They can |
| only be set inside a <a href="gloss.html#gloss.macroDefinitionBody">macro definition body</a>, |
| and are only visible from there. A local variable only exists for |
| the duration of a macro call. You can create and replace local |
| variables inside macro definition bodies with the <a href="ref_directive_local.html#ref.directive.local"><code>local</code> |
| directive</a>.</p> |
| </li> |
| |
| <li> |
| <p><strong>Loop variables</strong>: Loop |
| variables are created automatically by directives like <a href="ref_directive_list.html#ref.directive.list"><code>list</code></a>, and |
| they only exist between the start-tag and end-tag of the |
| directive. <a href="ref_directive_macro.html#ref.directive.macro">Macro</a> |
| parameters are local variables, not loop variables.</p> |
| </li> |
| </ul><p>Example: Create and replace variables with |
| <code class="inline-code">assign</code>:</p> |
| |
| <div class="code-wrapper"><pre class="code-block code-template"><#assign x = 1> <#-- create variable x --> |
| ${x} |
| <#assign x = x + 3> <#-- replace variable x --> |
| ${x}</pre></div><p>Output:</p> |
| |
| <div class="code-wrapper"><pre class="code-block code-output">1 |
| 4</pre></div><p>Local variables hide (not overwrite) ``plain'' variables of the |
| same name. Loop variables hide (not overwrite) local and ``plain'' |
| variables of the same name. For example:</p> |
| |
| <div class="code-wrapper"><pre class="code-block code-template"><#assign x = "plain"> |
| 1. ${x} <#-- we see the plain var. here --> |
| <@test/> |
| 6. ${x} <#-- the value of plain var. was not changed --> |
| <#list ["loop"] as x> |
| 7. ${x} <#-- now the loop var. hides the plain var. --> |
| <#assign x = "plain2"> <#-- replace the plain var, hiding does not mater here --> |
| 8. ${x} <#-- it still hides the plain var. --> |
| </#list> |
| 9. ${x} <#-- the new value of plain var. --> |
| |
| <#macro test> |
| 2. ${x} <#-- we still see the plain var. here --> |
| <#local x = "local"> |
| 3. ${x} <#-- now the local var. hides it --> |
| <#list ["loop"] as x> |
| 4. ${x} <#-- now the loop var. hides the local var. --> |
| </#list> |
| 5. ${x} <#-- now we see the local var. again --> |
| </#macro></pre></div><p>the output:</p> |
| |
| <div class="code-wrapper"><pre class="code-block code-output">1. plain |
| 2. plain |
| 3. local |
| 4. loop |
| 5. local |
| 6. plain |
| 7. loop |
| 8. loop |
| 9. plain2 |
| </pre></div><p>An inner loop variable can hide an outer loop variable:</p> |
| |
| <div class="code-wrapper"><pre class="code-block code-template"><#list ["loop 1"] as x> |
| ${x} |
| <#list ["loop 2"] as x> |
| ${x} |
| <#list ["loop 3"] as x> |
| ${x} |
| </#list> |
| ${x} |
| </#list> |
| ${x} |
| </#list></pre></div><p>the output:</p> |
| |
| <div class="code-wrapper"><pre class="code-block code-output"> loop 1 |
| loop 2 |
| loop 3 |
| loop 2 |
| loop 1</pre></div><p>Note that the value of a loop variable is set by the directive |
| invocation that has created it (the <code class="inline-code"><list |
| <em class="code-color">...</em>></code> tags in this case). There |
| is no other way to change the value of a loop variable (say, you can't |
| change its value with some kind of assignment directive). You can hide |
| temporarily a loop variable with another loop variable though, as you |
| have seen above.</p><p>Sometimes it happens that a variable hides the variable in the |
| data-model with the same name, but you want to read the variable of |
| the data-model. In this case you can use the <a href="dgui_template_exp.html#dgui_template_exp_var_special">special variable</a> |
| <code class="inline-code">globals</code>. For example, assume we have a variable |
| called <code class="inline-code">user</code> in the data-model with value ``Big |
| Joe'':</p> |
| |
| <div class="code-wrapper"><pre class="code-block code-template"><#assign user = "Joe Hider"> |
| ${user} <#-- prints: Joe Hider --> |
| ${.globals.user} <#-- prints: Big Joe --></pre></div><p>For information about syntax of variables please read: <a href="dgui_template_exp.html">The Template/Expressions</a></p><div class="bottom-pagers-wrapper"><div class="pagers bottom"><a class="paging-arrow previous" href="dgui_misc_userdefdir.html"><span>Previous</span></a><a class="paging-arrow next" href="dgui_misc_namespace.html"><span>Next</span></a></div></div></div></div> </div> |
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