CODEWITHSUNDEEP
iosobjective-c
Leem.fin
Leem.fin

Reputation: 42662

Access parent class instance variable from child class function

I have a parent class.

header file(Parent.h):

@interface Parent
@end

implementation file (Parent.m):

@interface Parent {
    // I defined a instance vaiable 'name'
    NSString *name;
    // another custom type instance variable
    School *mySchool;
}
@end

@implementation Parent
...
@end

Then, I have a Child class which inherits Parent.

header (Child.h):

@interface Child : Parent
-(void)doSomething;
@end

implementation file (Child.m):

@implementation Child
-(void)doSomething{
 // Here, how can I access the instance variable 'name' defined in Parent class?
 // I mean how to use the 'name' instance, not only get its value.
 // for example: call writeToFile:atomically:encoding:error: on 'name' here


  // tried to access mySchool defined in parent class
  // Property 'mySchool' not found on object of type 'Parent'
  School *school = [self valueForKey:@"mySchool"];
}
@end

How can I access instance variable defined in parent class from child class function?

==== Clarification ===

I mean how to use the 'name' instance, not only get its value. for example: call writeToFile:atomically:encoding:error: on 'name' here

Upvotes: 1

Views: 1406

Answers (2)

Cy-4AH
Cy-4AH

Reputation: 4605

It's not recommended now to user ivars in code and declare ivars in public header, but if you really-really need that, then you can use this old-style code:

//Parent.h
@interface Parent: NSObject {

@protected
    NSString *_name;
    School *_mySchool;
}
@end

//Parent.m
@implementation Parent
...
@end

//Child.h
@interface Child : Parent
-(void)doSomething;
@end

//Child.m
@implementation Child
-(void)doSomething{
  School *school = self->_mySchool;
  NSString *name = self->_name;
}
@end

Upvotes: 0

Andrey Chernukha
Andrey Chernukha

Reputation: 21808

By using key-value coding.

Setting:

[self setValue:@"Hello" forKey:@"name"];

Reading:

NSString* name = [self valueForKey:@"name"];
[name writeToFile:@"Filename"
       atomically:YES
         encoding:NSUTF8StringEncoding
            error:nil];

Upvotes: 1

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