Creating Guestbook List Screenlet's Delegate

A delegate is a Screenlet component that lets other classes to respond to a Screenlet’s actions. For example, Login Screenlet’s delegate lets the app developer implement methods that respond to login success or failure. Note that the reference documentation for each Screenlet that comes with Liferay Screens lists the Screenlet’s delegate methods.

You can also create a delegate for your own Screenlet. Guestbook List Screenlet should have a delegate protocol that defines the following methods:

• screenlet(_:onGuestbookListResponse:): Receives the GuestbookModel results when the server call succeeds. This lets app developers respond to a successful server call.
• screenlet(_:onGuestbookListError:): Receives the NSError object when the server call fails. This lets app developers respond to a failed server call.
• screenlet(_:onGuestbookSelected:): Receives the GuestbookModel when a user selects it in the list. This lets app developers respond to a guestbook selection by the user.

You’ll create this delegate in the same file as the Screenlet class. Later, you’ll finish creating the Screenlet class itself.

Follow these steps to create Guestbook List Screenlet’s delegate:

1. In the Project navigator, right-click the GuestbookListScreenlet folder and select New File. In the dialog that appears, fill out each screen as follows:

   • Select iOS → Source → Cocoa Touch Class, and click Next.
   • Name the class GuestbookListScreenlet, set it to extend BaseListScreenlet, select Swift for the language, and click Next.
   • Make sure the GuestbookListScreenlet folder and group is selected, as well as the Liferay Guestbook target (these should be selected by default). Click Create.

2. In the new GuestbookListScreenlet class, import LiferayScreens, make the class public, and delete any placeholder comments in the class body.

3. In between the import statements and the class declaration, add the following code:

   @objc public protocol GuestbookListScreenletDelegate : BaseScreenletDelegate {
   
       @objc optional func screenlet(screenlet: GuestbookListScreenlet,
                               onGuestbookListResponse guestbooks: [GuestbookModel])
   
       @objc optional func screenlet(screenlet: GuestbookListScreenlet,
                               onGuestbookListError error: NSError)
   
       @objc optional func screenlet(screenlet: GuestbookListScreenlet,
                               onGuestbookSelected guestbook: GuestbookModel)
   
   }
   

   This defines the GuestbookListScreenletDelegate protocol, which extends the BaseScreenletDelegate protocol. Delegates for custom Screenlets, like Guestbook List Screenlet, must extend BaseScreenletDelegate. The rest of GuestbookListScreenletDelegate defines the delegate methods you’ll use later to respond to the Screenlet’s events.

The contents of GuestbookListScreenlet.swift should now look like this:

import UIKit
import LiferayScreens

@objc public protocol GuestbookListScreenletDelegate : BaseScreenletDelegate {

    @objc optional func screenlet(screenlet: GuestbookListScreenlet,
                              onGuestbookListResponse guestbooks: [GuestbookModel])

    @objc optional func screenlet(screenlet: GuestbookListScreenlet,
                              onGuestbookListError error: NSError)

    @objc optional func screenlet(screenlet: GuestbookListScreenlet,
                              onGuestbookSelected guestbook: GuestbookModel)

}

public class GuestbookListScreenlet: BaseListScreenlet {

}

Nice work! Now you’re ready to complete the Screenlet class.