A protocol is a group of related properties and methods that can be implemented by any class.

Objective-C allows you to define protocols, which declare the methods expected to be used for a particular situation.

Lets understand this with the help of an example

// code of AddCountry.h file

#import <Foundation/Foundation.h>
 
// Protocol Name
@protocol AddCountryProtocolDelegate <NSObject>
// protocol method that called after country added in list
@required
- (void) CountryAddedToList;
@end
@interface AddCountry : NSObject
// hold country list.
@property (nonatomic, retain)NSMutableArray* CountryList;
// delegate object
@property (nonatomic,strong) id
<AddCountryProtocolDelegate>delegate;
// method that add country to list
-(void)addCountryToList:(NSString *)object;

@end
 

 
/// Code of AddCountry.m file
#import "AddCountry.h"
@implementation AddCountry
-(void)addCountryToList:(NSString *)object{

    if(_CountryList==nil){

     _CountryList=[[NSMutableArray alloc]init];
 
    }

    [_CountryList
addObject:object];

    [_delegate
CountryAddedToList];

}

@end
// code of view controller.h
#import <UIKit/UIKit.h>
#import "AddCountry.h"
@interface ViewController :
UIViewController<AddCountryProtocolDelegate>
- (IBAction)AddCountryButtonTap:(id)sender;
@property (strong, nonatomic) IBOutlet UITextField *TxtCountry;
@property(strong,nonatomic)AddCountry *CountryObj;
@end
// code of view controller.m
- (void)viewDidLoad {
    [super viewDidLoad];
// initialization of addcountry class  object and setting delegate.
_CountryObj=[[AddCountry alloc]init];

    _CountryObj.delegate=self;
}
- (IBAction)AddCountryButtonTap:(id)sender {
    [_CountryObj
addCountryToList:_TxtCountry.text];
}

 
#pragma mark  add country
class delegate method. this method is called after a country object added to
list.
-(void)CountryAddedToList{
    NSLog(@“Country
added to the list.");
    _TxtCountry.text=nil;
}