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iOS: starting it up


iOS and MacOS programming is based on objective-c, an object based increment of C which apple has created and maintained.

Objective-C has the many advantages over c when it comes to memory management, object defining. Although similar in spirit to c++, it is completely different syntactically as well as in implementation.

Objective-C has two files for every program: an interface file(*.h files) and an implementation file (*.m files)

The interface file has the declaration of the variables, properties and the methods.

In Objective-C, the process of calling a method is called passing messages.


iOS programming

iOS is an event based programming environment.

Views are the user interface, the glass pane of the app.

Controllers push data and images to the views and also collect user interaction data from the views. Controller is responsible for the apps behaviour. 

Model is the source of data or it is a data-store.




In the view and controller, there are different components:

1. Actions: a method/function linked to an event, such that the event will start the execution.
The return type of the method should be IBAction and the parameter should be sender.

  1. - (IBAction)restoreDefaults:(id)sender;
 
The IBAction keyword lets the storyboard identify the method to be an action method and shows in the list of methods to be linked to events. 
sender object refers to the object which triggered the event.

2. Outlets: a way to interact with the UI elements from the code.

Outlets are defined as properties in the interface file (.h), they are then used in the implementation file with any methods.

  1. @property (weak, nonatomic) IBOutlet UITextField *textField;
 
we can use the textField pointer to access the values and fields of the corresponding textfield element in the UI

3. Controls: UI elements which are used for controlling the flow, e.g: buttons, sliders, switch, etc.,

There are 3 categories of controls: Touch & drag events, editing events and value changed events.

4. Navigation controls: navigate between different views or pages within an app. (UINavigationController)

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(Main.storyboard) Storyboards can be used to define navigation, link between pages.

Create different views and link then using segues, which denote an event which triggers the transition from the current view to the next view.
Several types of Segues include:
1. Show: display new data in the existing view based on the layout.
2. Show detail: replaces the content in the current view controller stack. not all content may be replaced.
3. Present modally: one view controller presenting another controller modally, and waiting for an user action.
4. Popover Presentation: a view controllers is presented as a popover, linked to the current view controller.
5. Custom: implement by extending UIStoryBoardSegue
6. Unwind: reverse navigation.



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