Create a Controller Extension - Visualforce

Controller extensions are Apex classes. Creating your first Apex class is as easy as creating your first Visualforce page.

1. Click Setup | Develop | Apex Classes.
2. Click New.
3. Enter the following as the body of the Apex class:

   public class MyExtension {
       private final Account acct;
       
       public MyExtension(ApexPages.StandardController controller) {
           this.acct = (Account)controller.getRecord();
       }
       public String getTitle() {
           return 'Account: ' + acct.name + ' (' + acct.id + ')';
       }
   }

This is an Apex class named MyExtension that has an instance variable named acct. It has a constructor that retrieves the record from the controller parameter, and saves it in the acct variable. The class also has a method called getTitle() that returns a string containing the account’s name and identifier.

Most extensions have this form—with the constructor being the key ingredient. When the extension is used, Visualforce automatically invokes the constructor, passing in the controller for the page being viewed. This controller provides access to the record being viewed.