Getting Started with Guestbook List Screenlet

Before creating a Screenlet, you should know how you’ll use it. If you plan to use it in only one app, then you can create it in that app’s project. If you need to use it in several apps, however, then it’s best to create it in a separate project for redistribution. For information on creating Screenlets for redistribution, see the tutorial Packaging iOS Themes. Even though that tutorial is for packaging Themes, you can use the same steps to package Screenlets.

Since you’ll use Guestbook List Screenlet in only this app, you can create it in a new folder inside the app’s project. Create this folder now:

1. In the Finder, create the GuestbookListScreenlet folder inside the root project folder.

   

   Figure 1: The new `GuestbookListScreenlet` folder should be inside your root project folder.

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

   

   Figure 2: After adding the `GuestbookListScreenlet` folder, your project should look something like this.

Great! Now you have a folder to create Guestbook List Screenlet in. Before getting started, you should understand how pagination works in in list Screenlets.

Pagination

To ensure that users can scroll smoothly through large lists of items, list Screenlets support fluent pagination. Support for this is built into the list Screenlet framework. You’ll see this as you construct your list Screenlet. For example, several methods have parameters for the start row and end row of a page in the list.

Now you’re ready to begin creating the Screenlet!

Creating the Model Class

Liferay Screens typically receives entities from a Liferay DXP instance as a [String:AnyObject] dictionary, where String is the entity’s attribute and AnyObject is the attribute’s value. Although your Screenlet can use these dictionary objects, it’s often easier to create a model class that converts each into an object that represents the corresponding entity in the portal. Model classes are especially convenient for complex entities composed of many attribute-value pairs, like guestbooks in the Guestbook portlet.

Your model class must contain all the code necessary to transform each [String:AnyObject] dictionary that comes back from the server into a model object that represents a guestbook. This includes a public constant for holding each [String:AnyObject] dictionary, a public initializer that sets this constant, and a public property for each attribute value.

The model class you’ll create for Guestbook List Screenlet, GuestbookModel, creates GuestbookModel objects that represent guestbooks retrieved from the Guestbook portlet. You’ll create this model class in a separate folder outside of the GuestbookListScreenlet folder. In this case, it makes sense to organize your code this way because other Screenlets may also use the model class. For example, if a Screenlet that edits guestbooks existed, it would also need GuestbookModel objects. Putting the model class in a separate folder makes it clear that this class doesn’t belong exclusively to a single Screenlet.

Follow these steps to create Guestbook List Screenlet’s model class:

1. In the Finder, create the model folder inside your root project folder.

   

   Figure 3: The new `model` folder should be inside your root project folder.

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

   

   Figure 4: After adding the `model` folder, your project should look something like this.

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

   The new class now opens in the editor.

4. Replace the class file’s contents with this code:

   import UIKit
   
   @objc public class GuestbookModel: NSObject {
   
       public let attributes: [String:AnyObject]
   
       public var guestbookId: Int64 {
           return attributes["guestbookId"]?.int64Value ?? 0
       }
   
       public var groupId: Int64 {
           return attributes["groupId"]?.int64Value ?? 0
       }
   
       public var companyId: Int64 {
           return attributes["companyId"]?.int64Value ?? 0
       }
   
       public var userId: Int64 {
           return attributes["userId"]?.int64Value ?? 0
       }
   
       public var userName: String {
           return attributes["userName"] as? String ?? ""
       }
   
       public var createDate: Int64 {
           return attributes["createDate"]?.int64Value ?? 0
       }
   
       public var modifiedDate: Int64 {
           return attributes["modifiedDate"]?.int64Value ?? 0
       }
   
       public var name: String {
           return attributes["name"] as? String ?? ""
       }
   
       //MARK: Initializer
   
       public init(attributes: [String:AnyObject]) {
           self.attributes = attributes
       }
   
   }
   

This class creates GuestbookModel objects that represent guestbooks from the Guestbook portlet. The [String:AnyObject] dictionary contains the data of a guestbook retrieved from the portlet. The initializer sets this dictionary to the attributes property. Each computed property returns the value of a guestbook parameter in attributes. For example, the guestbookId property returns the value of the guestbookId parameter, the groupId property returns the value of the groupId parameter, and so on. To see how the Guestbook portlet defines these parameters, see the section on generating the portlet’s back end in the Liferay Web Application Learning Path.

Also note that each computed property defaults to an empty string or 0, depending on the property’s type, if the parameter contains a value that can’t be represented as that type. This prevents the app from crashing if the parameter doesn’t have an appropriate value. For example, if the guestbookId parameter contains nil, then the guestbookId property returns 0.

Great! Now you have a model class for guestbooks. Next, you’ll create the Screenlet’s UI.