The <apex:define> component is used within a Visualforce template to define specific content that should be inserted into a region specified by <apex:insert> in the template. It’s a key part of creating templated layouts in Visualforce.
Why Use <apex:define>?
- Helps structure and organize Visualforce pages using a common layout.
- Promotes reusability by separating layout from content.
- Allows developers to define page sections like headers, footers, and body content.
How It Works
- A template page contains
<apex:insert>tags to mark regions. - A content page that uses the template defines those regions using
<apex:define>.
Template Page (PageTemplate.page)
xmlCopyEdit<apex:composition template="StandardLayout">
<apex:define name="body">
<h1>This is the body content</h1>
</apex:define>
<apex:define name="footer">
<p>This is the footer section</p>
</apex:define>
</apex:composition>
Template Layout (StandardLayout.page)
xmlCopyEdit<apex:component>
<apex:insert name="body"/>
<hr/>
<apex:insert name="footer"/>
</apex:component>
Key Attributes
name: The name of the section you want to define (must match the name used in<apex:insert>).- Content inside
<apex:define>replaces the corresponding<apex:insert>in the template.
Use Cases
- Consistent Layouts: Maintain the same layout across multiple Visualforce pages.
- Dynamic Page Sections: Customize specific regions of a page while reusing common elements.
- Theming and Branding: Easily apply consistent headers/footers across an application.