Freemarker templates double inheritence (child extends parent extends grandparent)

Question

Freemarker templates double inheritence (child extends parent extends grandparent)

255 Views Asked by Geoffrey De Smet At 06 April 2025 at 00:13

In Freemarker, how can I create a template that inherits from a template that itself inherits?

Single inheritance works fine with the <#nested> tag:

File base.ftl:

<#macro layout>
<html lang="en">
  <head>...</head>
  <body>
    <div>... (navigation bar)</div>
    <div class="container">
      <#nested>
    </div>
  </body>
</html>
</#macro>

File normalBase.ftl:

<#import "base.ftl" as base>

<@base.layout>
  <div class="row">
    <div class="col-md-9">
      ${content.body}
    </div>
    <div class="col-md-3">
       <p>Latest releases</p>
       <ul>....</ul>
    </div>
  </div>
</@base.layout>

How do I turn this into double inheritance where useCaseBase.ftl extends normalBase.ftl which extends base.ftl?

Original Q&A

There are 2 best solutions below

emesday On 23 November 2022 at 06:05

I tried to implement extends and block like Jinja2.

extends.ftl for defining macros.

<#if !blocks??>
    <#assign blocks = {} />
</#if>

<#macro extends ftl>
    <#nested />
    <#include ftl />
</#macro>

<#macro replace name>
    <#local value>
        <#nested />
    </#local>
    <#assign blocks += {name: value} />
</#macro>

<#macro block name>
    <#if blocks[name]??>
        <!-- replaced ${name} -->
        ${blocks[name]}
    <#else>
        <!-- default ${name} -->
        <#nested />
    </#if>
</#macro>

base.ftl for layout

<#import "extends.ftl" as layout />

<!DOCTYPE html>
<html>
<head>
    <title>A demo of FreeMarker extends directive</title>
</head>
<body>
<@layout.block "message">
    This is default message in base.ftl
</@layout.block>
</body>
</html>

finally, index.ftl like this:

<#import "extends.ftl" as layout />

<@layout.extends "base.ftl">
    <@layout.replace "message">
        This is the message from index.ftl
    </@layout.replace>
</@layout.extends>

Take a look at https://github.com/emesday/freemarker-extends .

**Geoffrey De Smet** · Accepted Answer

This works like a charm:

File base.ftl:

<#macro layout>
<html lang="en">
  <head>...</head>
  <body>
    ... // Shared navigation bar
    <div class="container">
      <#nested>
    </div>
    ... // Shared footer
  </body>
</html>
</#macro>

<@layout>
  ${content.body}
</@layout>

File normalBase.ftl:

<#import "base.ftl" as parent>

<#macro layout>
    <@parent.layout>
        <div class="row">
            <div class="col-md-9">
                <#nested>
            </div>
            <div class="col-md-3">
                ... // Shared sidebar
            </div>
        </div>
    </@parent.layout>
</#macro>

<@layout>
    ${content.body}
</@layout>

File useCaseBase.ftl:

<#import "normalBase.ftl" as parent>

<@parent.layout>
    ${content.body}
    ... // Shared content between all use case pages
</@parent.layout>

Now I can create *.adoc pages with jbake-type set to either base, normalBase or useCaseBase and it works.

Freemarker templates double inheritence (child extends parent extends grandparent)

There are 2 best solutions below

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