ActionFunction is a component, which provides support for invoking controller action methods directly from JavaScript code with the use of AJAX request.
An <apex:actionFunction> component must be a child of an <apex:form> component.
Unlike <apex:actionSupport>, which only provides support for invoking controller action methods from other Visualforce components, <apex:actionFunction> defines a new JavaScript function which can then be called from within a block of JavaScript code.
Beginning with API version 23 you can't place <apex:actionFunction> inside an iteration component — <apex:pageBlockTable>, <apex:repeat>, and so on. Put the <apex:actionFunction> after the iteration component, and inside the iteration put a normal JavaScript function that calls it.
If we want to use actionFunction, the first step is setting off a name (name=”MyActionFunction”). It is the only required attribute in this component. When we want to call our function, we call it by name.
Next step is to set action. The action method is invoked when the actionFunction is called by a DOM event elsewhere in the page markup. Use merge-field syntax to reference the method. For example, action="{!save}" references the save method in the controller. If an action is not specified, the page simply refreshes.
Attribute rendered can be used to activate or to deactivate your actionFunction. You can use a formula here.
Attribute reRender helps us to update only chosen (by id) parts of the page when the action is completed.
With help of oncomplete it is possible to set, what will happen next.
The JavaScript is invoked when the onbeforedomupdate event occurs – that is when the AJAX request has been processed, but before the browser's DOM is updated.
In the timeout we can set the amount of time (in milliseconds) before an AJAX update request should time out.
Attribute namespace helps you to set necessary namespace for your function, but if this attribute is not added, the namespace will be generated automatically.
Like in most other components, you can set id for your actionFunction and allow the actionFunction component to be referenced by other components in the page.
In focus attribute you can put the ID of the component that is in focus after the AJAX request completes.
Attribute status is the ID of an associated component that displays the status of an AJAX update request.
Setting immediate="true" we can specify whether the action associated with this component should happen immediately, without processing any validation rules associated with the fields on the page.
<!-- Page: -->
/*** Controller ***/
