Core Layer of Liferay Screens for iOS

The Core is the micro-framework that lets developers write Screenlets in a structured and isolated way. All Screenlets share a common structure based on the Core classes, but each Screenlet can have a unique purpose and communication API.

Figure 1: Here's the core layer of Liferay Screens for iOS.

From right to left, these are the main components:

• BaseScreenletView: The base class for all Screenlet View classes. Its child classes belong to the Theme layer. View classes use standard XIB files to render a UI and then update it when the data changes. The BaseScreenletView class contains template methods that child classes may overwrite. When developing your own Theme from a parent Theme, you can read the Screenlet’s properties or call its methods from this class. Any user action in the UI is received in this class, and then redirected to the Screenlet class.

• BaseScreenlet: The base class for all Screenlet classes. Screenlet classes receive UI events through the ScreenletView class, then instantiate Interactors to process and respond to that UI event. When the Interactor’s result is received, the ScreenletView (the UI) is updated accordingly. The BaseScreenlet class contains a set of template methods that child classes may overwrite.

• Interactor: The base class for all Interactors that a Screenlet supports. The Interactor class implements a specific use case supported by the Screenlet. If the Screenlet supports several use cases, it needs different Interactors. If the Interactor needs to retrieve remote data, it uses a Server Connector to do so. When the Server Connector returns the operation’s result, the Interactor returns that result to the Screenlet. The Screenlet then changes the ScreenletView (the UI) status.

• ServerConnector: The base class for all Liferay Connectors that a Screenlet supports. Connectors retrieve data asynchronously from local or remote data sources. The Interactor classes instantiate and start these Connector classes.

• SessionContext: An object (typically a singleton) that holds the logged in user’s session. Apps can use an implicit login, invisible to the user, or a login that relies on explicit user input to create the session. User logins can be implemented with Login Screenlet. For more information, see the tutorial on accessing the session in iOS.

• LiferayServerContext: A singleton object that holds server configuration parameters. It’s loaded from the liferay-server-context.plist file. Most Screenlets use these parameters as default values.

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