flexonrails.net

This is the fourth post in a series that covers certain features of Issue Tracker sample app (view, source) that I added to the Flex RoR SDK.

The first post explained how to set up the application.

The second post covered how you can get WebORB for Rails to return typed objects to Flex using the [RemoteClass] metadata tag.

The third post covered how to use ActiveRecord Associations with WebORB.

This post explains how you can invoke ActiveRecord methods directly inside of a Flex client.

WebORB gives you the ability call ActiveRecord methods from inside of Flex. Here is all you have to do to make this happen:

1. To do this you first set up a RemoteObject in Flex just like you would for any other service. For example, the following code is from the Services.mxml file in flex_issue_tracker2 project:

<mx:RemoteObject id="userService" destination="userServiceImpl"
		    showBusyCursor="true
                       result="event.token.resultHandler( event );"
		    fault="event.token.faultHandler( event );">
</mx:RemoteObject>

2. Open up the remoting-config.xml file (located in C:\rails\rails_issue_tracker2\config\WEB-INF\flex) and map the RemoteObject directly to an ActiveRecord class. This is the mapping for the userService RemoteObject:

    <destination id="userServiceImpl">
        <properties>
            <source>User</source>
        </properties>
    </destination>

Now when you make a method call on the userService RemoteObject it as though you are making the call directly on the User ActiveRecord class. This makes it possible to do some interesting things, such as calling ActiveRecord dynamic finder methods directly on the userService, which is what is currently happening in the UserDelegate class in Flex:

package com.rxr.issuetracker.business
{
import mx.rpc.IResponder;
import com.adobe.cairngorm.business.ServiceLocator;

public class UserDelegate
{
	private var responder : IResponder;
	private var service : Object;

	public function UserDelegate(responder : IResponder)
	{
	      this.service = ServiceLocator.getInstance().getService( "userService" );
	      this.responder = responder;
	}

	public function loginUser(username : String, password : String) : void
	{
	      var call : Object = service.find_by_username_and_password(username, password);
	      call.resultHandler = responder.result;
	      call.faultHandler = responder.fault;
	}

	public function registerUser(username : String, password : String) : void
	{
	      var call : Object = service.find_or_create_by_username_and_password(username, password);
	      call.resultHandler = responder.result;
	      call.faultHandler = responder.fault;
	}
}
}

ActiveRecord dynamic finders are finder methods that are automatically generated by Rails based on the column names in the table that the ActiveRecord wraps. For example, the users table has three columns: id, username, and password. So, the User ActiveRecord class automatically generates a method called find_by_username, and a method called find_by_username_and_password, and so on. Click here to read an article that provides an in-depth explanation of how dynamic finders work.

As you can see, there are two dynamic finders that are currently being used in the UserDelegate class: find_by_username_and_password(username, password); in the loginUser method which finds an existing user, and find_or_create_by_username_and_password(username, password); in the registerUser method which creates a new user if it does not find one that matches the provided username and password.

Ok, now that you know how invoke ActiveRecord methods inside of Flex I should note that I think that you should only do this where it really makes sense to do so. The obvious drawback to this approach is that you have to make a call to the server for each method that you invoke. In general, it is best to keep this type of logic in a server-side service class (like the ProjectService and the IssueService). I’ve only included this functionality in Issue Tracker Sample app to show that it is possible. I plan to remove this code in the next update of the application and move into a UserService class.