The “iPhone Apps” also termed as “iOS apps” works on the concept of Model View Controller (MVC) framework pattern. Almost every application built in iPhone works on MVC architecture design.
The main idea behind using MVC style in building iPhone Apps is that combination of the three roles that is, Model; View; and Controller results into the best user friendly mobile display interface. Working together in an application helps to create and handle every user interface. They act as the actors performing main role to make apps work properly.
Brief Introduction of MVC pattern:
The role of Model represents the data or information in the application. It is mainly responsible to validate, manage and sort the data provided.
User Interface “View” is exactly what the end user see on the application and performs interactions with the displayed data application.
Views are created using Apple class including “UIView”. XIB file is also one of the medium to represent ‘view’ and display the layout for elements through the “Builder” interface.
UIView are views created in XCode and represent the view displayed to the user. UIViewController is a controller created in XCode.
The actor “Controller”takes care of the communication between the view and the model. It accepts the data from the model, and connects it to the view to display the exact end result.
Controller also receive the modified data resulted from the interaction by user or any other case; and further send it back to the model.
Great point is that the actor Model and View never interconnect with each other:
When coming to the thought of model and view communication; the real scenario is that they never know anything about each other. It is the most beautiful part of the MVC architecture. This modular design divides the role of Model and View in real; and thus any changes in the application can be done with minor software bugs.
To summarize MVC pattern; it is concluded that MVC architecture is a masterpiece to rule all the applications in iPhone.
Lifecycle of View Controllers:
There is a lifecycle of any event or procedure that is shown in the application. A complete step-by-step set of action is performed from the starting point of the application displayed on output display till the end. Firststep is that “UIViewController” is loaded into the memory and it set up the UIView to show the outlook to the users.
As soon as the user moves on from that particular view, UIView shuts down suddenly and thus UIViewController is unloaded from the memory.
UIViewController class supports several eventsto achieve certain task during execution of the apps. There are certain events that are useful to override and execute the code at the time of lifecycle of ViewController:
• ViewDidLoad:This event occurs after view loads into the memory.
• ViewWillAppear:In this method, the view is rendered to the user.
• ViewWillDisappear:View is about to be erased from the screen.
• ViewDidAppear:View is just shown to the end user.
• ViewDidDisappear:The view disappeared from the display.
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