Visualforce Developer Guide

Introducing Visualforce
Tools for Visualforce Development
Getting a Quick Start with Visualforce
Customizing the Appearance and Output of Visualforce Pages
Standard Controllers
Standard List Controllers
Custom Controllers and Controller Extensions
Advanced Examples
Override Buttons, Links, and Tabs with Visualforce
Using Static Resources
Creating and Using Custom Components
Dynamic Visualforce Bindings
Using Dynamic References with Standard Objects
Using Dynamic References with Custom Objects and Packages
Reference Apex Maps and Lists
Working with Field Sets
Dynamic References to Global Variables
Dynamic References to Static Resources Using $Resource
Dynamic References to Action Methods Using $Action
Dynamic References to Schema Details Using $ObjectType
Dynamic Visualforce Components
Integrate Email with Visualforce
Visualforce Charting
Creating Maps with Visualforce
Render Flows with Visualforce
Templating with Visualforce
Developing Salesforce Apps with Visualforce
Adding Visualforce to a Salesforce AppExchange App
Using JavaScript in Visualforce Pages
Communicating Across the DOM with Lightning Message Service
Visualforce Best Practices
Standard Visualforce Component Reference
Appendices
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Dynamic References to Action Methods Using $Action

The $Action global variable allows you to dynamically reference valid actions on an object type, or on a specific record. The most likely way to make use of this is to create a URL to perform that action.

For example, you can use the expression {!URLFOR($Action[objectName].New)} in an <apex:outputLink>, with a controller method getObjectName() that provides the name of the sObject.

Here’s an example that does exactly that. The controller extension queries the system to learn the names of all the custom objects accessible to the user, and presents a list of them, along with links to create a new record. First, create a controller extension named DynamicActionsHandler:
There are a few things of interest in this extension:
  • The loadCustomObjects method uses Apex schema methods to get metadata information about available custom objects. The Schema.getGlobalDescribe method is a lightweight operation to get a small set of metadata about available objects and custom settings. The method scans the collection looking for items with names that end in “__c”, which indicates they are custom objects or settings. These items are more deeply inspected using getDescribe, and selected metadata is saved for the custom objects.
  • Using if(obj.endsWith('__c')) to test whether an item is a custom object or not may feel like a “hack”, but the alternative is to call obj.getDescribe().isCustom(), which is expensive, and there is a governor limit on the number of calls to getDescribe. Scanning for the “__c” string as a first pass on a potentially long list of objects is more efficient.
  • This metadata is saved in an inner class, CustomObjectDetails, which functions as a simple structured container for the fields to be saved.
  • CustomObjectDetails implements the Comparable interface, which makes it possible to sort a list of custom objects details by an attribute of each object, in this case, the custom object’s name.
Now create a Visualforce page with the following markup:
On a page that hasn’t been assigned a specific record, the only two useful actions available are New and List. On a page that queries for a record, the $Action global variable provides methods such as View, Clone, Edit, and Delete. Certain standard objects have additional actions that make sense for their data types.