CODEWITHSUNDEEP
objective-ccocoa-touch
Snowman
Snowman

Reputation: 32071

Access a UITableView from child class

I have two view controllers, class A and class B. Class B is a subclass of class A. Class B has a UITableView defined, and in the parent class A, I want to be able to [table reloadData]. So I want to access a member variable of class Bfrom parent class A. I tried doing the whole forward declaration thing but that didn't work out. In class B, I put @class A. And then in my class A, I tried declaring a class B object to access the table like this: B *bView=[B alloc] init]; [bView.table reloadData] //doesn't work, I get error: Receiver B is a forward class and corresponding @interface may not exist

So not sure why that's not working, but maybe I shouldnt even be doing it like this. Since its a parent class, is there a better way to access child member variables?

Upvotes: 0

Views: 155

Answers (2)

Warren Burton
Warren Burton

Reputation: 17382

The parent gets no implicit access to its childs member variables. So from A's point of view B is any old object.

If B is a subclass of A then you should be doing this in B.h

#import "A.h"

@interface B:A
{
...
}
@property (readwrite,retain) UITableView *table;

And if you wish to use B in A then you can do this in "A.h" in case where you want a B member

@class B

@interface A:Foo
{
B* bar;
}

Or don't bother with the forward declaration if you don't want a B member

In both cases in A.m

#import "B.h"

You can also use #include guards to stop double imports.

#ifndef AHEADER_H
#define AHEADER_H

@interface A:Foo
...
@end

#endif

No matter how many times you use #import A.h it will only get imported once.

Upvotes: 2

Cameron Spickert
Cameron Spickert

Reputation: 5200

You should not need to do this. Why not just reload the table in the subclass implementation? You can override Class A's methods in Class B if you want to add some new behaviors to existing code.

Upvotes: 0

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