inheritance & objective-c - objective-c

Question

this is my h file:
#import <Foundation/Foundation.h>
#interface Base : NSObject
#end
this is my m file:
#import "Base.h"
#interface Base()
#property (nonatomic) int number;
#end
#implementation Base
-(void) setNumber: (int) p_number
{
self.number = p_number;
}
#end
this is what i want to accomplish
an h file:
#import <Foundation/Foundation.h>
#import "Base.h"
#interface Derived : Base
#end
and to do this in the m file
#import "Derived.h"
#implementation Derived
- (void) foo
{
self.number= 7;
}
#end
this of course results in error, please answer with a code that allows me to call the base property without placing the definition in the h file
thanks

Answer 1

Asking people to answer only with code is not a good idea. Why not ask for an explanation of what's wrong, so that you can fix this error and tons of similar errors in the future yourself?
The problem here is that you don't declare your property in the base header. If you don't want to do that, you can declare it in your subclass' implementation file as an extension of your base class:
Derived.m
#import "Derived.h"
#interface Base ()
#property (nonatomic) int number;
#end
#implementation Derived
- (void) foo
{
self.number= 7;
}
#end

Answer 2

You could use the same approach that Apple uses with UIGestureRecognizerSubclass.h
e.g. Create
// BaseSubclass.h
#interface Base (ForSubclassEyesOnly)
#property (nonatomic, assign) NSInteger number;
#end
You'll need to silence the compiler with
#implementation Base (ForSubclassEyesOnly)
#dynamic number;
#end
Now any class that want's to use these properties/call methods just includes this header.
e.g
#import "Derived.h"
#import "BaseSubclass.h"
#implementation Derived
- (void) foo
{
self.number = 7;
}
#end