Creating Guestbook List Screenlet's Connector

Connectors are Screenlet components that make server calls. Non-list Screenlets don’t require Connectors–they can make server calls in Interactors instead. Connectors, however, provide a layer of abstraction by making the server call outside the Interactor. This leaves the Interactor to instantiate the Connector and receive the server call’s results. List Screenlets exploit this architectural advantage by requiring Connectors.

First, you’ll create a folder for the Connector.

Creating Your Connector’s Folder

Follow these steps to create your Connector’s folder:

1. In the Finder, create the Connector folder inside your project’s GuestbookListScreenlet folder.

2. Drag and drop the Connector folder from the Finder into your Xcode project, under the GuestbookListScreenlet folder. In the dialog that appears, select Copy items if needed, Create groups, and the Liferay Guestbook target. Then click Finish. The Connector folder now appears in your project.

   

   Figure 1: The new `Connector` folder should be inside the Screenlet's folder.

Now you’re ready to create the Connector.

Creating the Connector

List Screenlet Connectors must extend the PaginationLiferayConnector class, which Liferay Screens provides to enable most of the functionality required by list Screenlet Connectors. Extending this class lets you focus on the functionality unique to your Connector. Your list Screenlet’s Connector class must contain any properties it needs to make the server call, and an initializer that sets them. To support pagination, the initializer must also contain the following arguments, which you’ll pass to the superclass initializer:

• startRow: The number representing the page’s first row.
• endRow: The number representing the page’s last row.
• computeRowCount: Whether to call the Connector’s doAddRowCountServiceCall method (you’ll learn about this method shortly).

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

1. In the Project navigator, right-click the Connector 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 GuestbookListPageLiferayConnector, set it to extend PaginationLiferayConnector, select Swift for the language, and click Next.
   • Make sure the Connector folder and group is selected, as well as the Liferay Guestbook target (these should be selected by default). Click Create.

2. In the new class, import LiferayScreens and add a public Int64 constant called groupId. This constant holds the ID of the site the Connector retrieves guestbooks from. Your Connector should now look like this:

   import UIKit
   import LiferayScreens
   
   class GuestbookListPageLiferayConnector: PaginationLiferayConnector {
   
       public let groupId: Int64
   
   }
   

3. Create an initializer that takes the arguments startRow, endRow, computeRowCount, and groupId. In this initializer, set the groupId constant to the corresponding argument, then call the superclass initializer with the remaining arguments. Add the initializer as follows:

   public init(startRow: Int, endRow: Int, computeRowCount: Bool, groupId: Int64) {
       self.groupId = groupId
   
       super.init(startRow: startRow, endRow: endRow, computeRowCount: computeRowCount)
   }
   

4. Override the doAddPageRowsServiceCall method to make the server call that retrieves guestbooks from the portlet. This method must call the Guestbook SDK service method getGuestbooksWithGroupId, which retrieves guestbooks. To do this, you must first create a LRGuestbookService_v7 instance from the session. Then call the service’s getGuestbooksWithGroupId method with groupId, startRow, and endRow:

   public override func doAddPageRowsServiceCall(session: LRBatchSession, startRow: Int, endRow: Int, 
       obc: LRJSONObjectWrapper?) {
           let service = LRGuestbookService_v7(session: session)
   
           do {
               try service!.getGuestbooksWithGroupId(groupId, start: Int32(startRow), end: Int32(endRow))
           }
           catch {
               // ignore error: the service method returns nil because 
               // the request is sent later, in batch
           }
   
   }
   

   Note that you don’t need to do anything in the catch statement because the request is sent later, in batch. The session type LRBatchSession handles this for you. You’ll receive the request’s results elsewhere, once the request completes.

5. Override the doAddRowCountServiceCall method to make the server call that retrieves the total number of guestbooks from the portlet. This enables pagination. This method must call the Guestbook SDK service method getGuestbooksCount, which retrieves the total number of guestbooks. To do this, you must first create a LRGuestbookService_v7 service instance from the session. Then call the service’s getGuestbooksCount method with groupId:

   override public func doAddRowCountServiceCall(session: LRBatchSession) {
       let service = LRGuestbookService_v7(session: session)
   
       do {
           try service!.getGuestbooksCount(withGroupId: groupId)
       }
       catch {
           // ignore error: the service method returns nil because 
           // the request is sent later, in batch
       }
   }
   

   As in the previous step, you don’t need to do anything in the catch statement.

Awesome! Your Connector is finished. Now you’re ready to create the Interactor.