init function and id return type in objective c

Init Function And ID return type in Objective C

What is Init Function?

Init Function are used to initialize the instance variable of class with starting value or initial value at time of creation of object. As you heard about the constructor function in programming languages C,C++. Constructor has name as the name of class. Constructor Function has no any return type.

Example of constructor in C++: class student

{

private :

int StudentRollNo;

void Student()

{

StudentRollNo=101;

}

}

Creation of object is done below:

Student student1=new Student();

During this time it is called automatically or set to initial value and that can be manipulate further accordingly.

Think for some time that init function is working in same way like constructor.

Now come into Objective C Part.

In an Objective C init function has always id data type or return type.The init function return type is not specific to integer,string due to its initialization at run time what value will user enter these are not sure or not known to compiler therefore id return type is used. Also Objective C is dynamic language.

We come lator on it first solve the simple example of init function.

In Student.h class

@interface Student:NSObject

{

NSString *studentname;

}

@property(nonatomic,strong) NSString *StudentName;

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

-(void)printName;

@end

In Student.m class

@implementation Student

@synthesize StudentName=_StudentName;

-(id)initWithStudentName:(NSString *)StudentName

{

studentname=StudentName;

return self;

}

-(void)printName

{

NSLog(@”The name of student is %@”,studentname);

}

@end

In main section

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

{

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

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

[student1 showInformation];

[pool drain];

Return 0;

}

id type in Objective C

id type in Objective C is collection of all information of data types like NSString,NSInteger etc. in one type.When you using type of object as id data type then you are not sure about the type of data you entered or what a method could return. If you use another type instead of id then at compile time compiler compile it but run time it causing big error of different type.Type Conversion are possible but if you do not know type then how you convert.

In general you can say Objective C is Dynamic Language .A call to specific type return at run time if you do not know about type.

Example:

In Student.h class

@interface Student

{

Id *studentname;

Id *studentid

}

@property(nonstomic,strong)id *StudentName;

@property(nonatomic,strong)id *StudentId;

-(void)StudentName:(NSString *)StudentName;

-(void)StudentID:(NSInteger *)StudentID;

@end

In Student.m class

@implementation Student

@synthesize StudentName=_StudentName;

@synthesize StudentID=_StudentID;

-(void)StudentName:(NSString *)StudentName

{

studentname=StudentName;

NSLog(@”The student name is:%@”,studentname);

}

-(void)StudentID:(NSInteger *)StudentID

{

studentid=StudentID;

NSLog(@”Student ID is :%d”,studentid);

}

 In main section

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

{

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

Student student1=[[Student alloc]init];

[student1 printStudentName:@”abc”];

[student1 printStudentID:101];

[pool drain];

Return 0;

}

Now in above case the type of data to StudentName instance variable is NSString but id uses means automatically invoke at run time and compiler nothing knows about it.

I hope you like my tutorial.

Ok lets we meet in our next tutorial.

 My next tutorial will be Dynamic Binding.