self and super in objective c

Self,Super Keyword in Objective C

In an Objective C Objects can send messages to own. You think that how object can send message to own. When I say send message to object then think that method call with corresponding objects.

Why SELF keyword is required?

When there is calling of message required inside from a method with same object then it can be done through self keyword which send message to own.  You do not need to call again and again simple one call from main method and all other call done automatically from indside a method but the control will reach after execution of method at that place from the point where call is made.

In below example we want to set student name at run time(called at console) Also we want to check how many friend that student whose name is set. We call from inside the setStudentName method.

Example:

In Student.h class

@interface Student:NSObject

{

NSString studentname,friendname;

}

@property(nonatomic,strong)NSString *StudentName;

@property(nonatomic,strong)NSString *FriendName;

-(void)setStudentName;

-(void)studentFriend;

-(void)showInformation;

@end

In Student.m class

@implementation Student

@synthesize StudentName=_StudentName;

@synthesize FriendName=_FriendName;

-(void)setStudentName

{

NSLog(@”Enter Student your name:”);

Scanf(“%d”,StudentName);

Studentname=self.StudentName;

[self studentFriend];

}

-(void)studentFriend

{

NSLog(@”Enter your Friend Name:”);

Scanf(“%d”, FriendName);

friendname=self.FriendName;

}

-(void)showInformation

{
NSLog(@”%@ has Friend Name: %@ is”studentname,friendname);

}

Main Class

Int main(int argc,const char * argv[])

{

NSAutorealesePool *pool=[[NSAutorealesePool alloc]init];

Student *student1=[[Student alloc]init];

[student1 setStudentName];

//We do not need to write here calling friendname method it is automatically called from same object from which above method is called.

[student1 showInformation];

[pool drain];

Return 0;

}

Now you can see from above program the method friendStudent is automatically called with same object inside a setStudentName method.

Super Keyword

Next we come up with super keyword. When a derived class is inherited from base class

And call is made up with derived class object then you can also use that object to call the base class method.

In Teacher.h class

@interface Teacher:NSObject
@property(nonatomic,strong)NSString *TeacherName;

-(void)checkStudentTeacher:(NSString *)TeacherName;

@end;

In Teacher.m class

@synthesize TeacherName=_TeacherName;

-(void)checkStudentTeacher:(NSString *)TeacherName

{

NSLog(@"The %@ Student is studied by %@ Teacher",studentname,TeacherName);

}
-(void)showResult
{
[self checkStudentTeacher:@"Suraj"];
}

In Student.h class

 @interface Student:Teacher
{
NSString *studentname;
}
@property(nonatomic,strong)NSString *StudentName;

-(id)initWithTeacherName:(NSString *)StudentName;

-(void)showInformation;

@end

In Student.m class

@implementation Student

@syntheisize StudentName=_StudentName;

-(id)initWithStudentName:(NSString *)StudentName;

{

studentname=StudentName;

Return self;

}

-(void)showInformation

{

[super checkResult];

}

In Main Class

 Int main(int argc,const char * argv[])

{

NSAutorealesePool *pool=[[NSAutorealesePool alloc]init];

Student *student1=[[Student alloc]initWithStudentName:@"abc”];

[student1 showInformation];

[pool drain];

Return 0;

}

In the above example Student class object is created.With the help of this object first call is made up to method showInformation of Student class.Due to inheritance same pointer or object is call in base class with super keyword used to 

Then Control is reached at the end same location in inherit class at end where call is made up.

I hope you like my tutorial .

My next tutorial is about init function and id data types.