Protocal definition and Example

@Protocal: To create a own protocal delegate

 protocols declare methods that can be implemented by any class. These classes are said to conform to the protocol. They are like interfaces in Java

Formal protocols are declared with a @protocol block.

• Informal protocols can be implemented in terms of a @protocol block with all the methods being@optional or with a category of NSObject

Delegates are very useful to control transfer within the array of view controllers in app manually. Using delegates you can manage the control flow very well.

here is small example of own delegates....

1. Create a protocol class.... (.h only)

file--->new --->objective -c protocal (give name)

Ex:SampleDelegate

SampleDelegate.h

#import <UIKit/UIKit.h>

@protocol SampleDelegate // protocal name

@optional

#pragma Home Delegate

-(NSString *)getViewName;

@end

2. Import above protocol class in the class whom you want to make delegate of another class. Here in my ex. I m using AppDelegate to make delegate of The HomeViewController's Object.

also add above DelegateName in Delegate Reference < >

ownDelegateAppDelegate.h

#import "SampleDelegate.h"

@interface ownDelegateAppDelegate : NSObject <UIApplicationDelegate, SampleDelegate>

{

}

ownDelegateAppDelegate.m

//setDelegate of the HomeViewController's object as

[homeViewControllerObject setDelegate:self];

//add this delegate method definition

-(NSString *)getViewName

{

return @"Delegate Called";

}

HomeViewController.h

#import

#import "SampleDelegate.h" // protocal header file.

@interface HomeViewController : UIViewController 

{

id<SampleDelegate>delegate;

}

@property(readwrite ,assign) id<SampleDelegate>delegate; //set the property

@end

HomeViewController.h

-(void)viewDidAppear:(BOOL)animated

{

[super viewDidAppear:animated];

 UILabel *lblTitle = [[UILabel alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

 lblTitle.text = [delegate getViewName];

lblTitle.textAlignment = UITextAlignmentCenter;

  [self.view addSubview:lblTitle];

}

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