Objective-C protocol and Delegation

Objective-c Protocol delegate implements Protocol-the Protocol. After using this protocol, you must follow this Protocol. The methods required by the Protocol must be implemented. Delegate delegate-delegation, as its name implies, is to entrust others to handle affairs, that is, when one thing happens, it will not be handled by others. When a view contains B view and B view needs to modify the View Interface, delegation is required. Steps 1 are required. First set a protocol Protocol 2. Method 3 in the implementation protocol of a view. B View sets a delegate variable limit 4. Set the delegate variable of B view to a view, which means that B view delegates a view to do things. Limit 5. After an event occurs, use the delegate variable to call the Protocol method in a view. Example: 
 B _view.h: Protocol @ protocol uibviewdelegate <nsobject>
@ Optional
-(Void) ontouch :( uiscrollview *) scrollview; // declares the Protocol method.
@ End
@ Interface bview: uiscrollview <uiscrollviewdelegate>
{
ID <uibviewdelegate> _ touchdelegate; // sets the delegate variable.
}
@ Property (nonatomic, assign) ID <uibviewdelegate> _ touchdelegate;
@ End
B _view.mm:
@ Synthesize _ touchdelegate;
-(ID) initwithframe :( cgrect) frame {
If (Self = [Super initwithframe: frame]) {
// Initialization code
_ Touchdelegate = nil;
}
Return self;
}
-(Void) touchesbegan :( nsset *) touches withevent :( uievent *) event
{
[Super touchesbegan: touches withevent: event];
Else if (_ touchdelegate! = Nil & [_ touchdelegate respondstoselector: @ selector (ontouch :)] = true)
[_ Touchdelegate ontouch: Self]; // call protocol delegate
}
@ End paia_view.h: audience @ interface aviewcontroller: uiviewcontroller <uibviewdelegate>
{
Bview * m_bview;
}
@ End

 A_view.mm:
-(Void) viewwillappear :( bool) animated
{
M_bview. _ touchdelegate = self; // sets the delegate
[Self. View addsubview: m_bview];
Token}
-(Void) ontouch :( uiscrollview *) scrollview
{
// Implementation Protocol
}