Anonymous

//
//  Entity.h
//  inheritance
//
#import <Foundation/Foundation.h>

@interface Entity : NSObject {
}

- (void)sayPleaseWork;

@end


//
//  Entity.m
//  inheritance
#import "Entity.h"

@implementation Entity

- (void)sayPleaseWork
{
	NSLog(@"Please work.");
}

@end


//
//  Action.h
//  inheritance

#import "Entity.h"

@interface Action : NSObject {
	Entity	*__anEntity;
}

- (Entity *)anEntity;
- (void)setAnEntity:(Entity *)newAnEntity;

@end

//
//  Action.m
//  inheritance
#import "Action.h"

@implementation Action

// init
- (id)init
{
    if (self = [super init]) {
//        [self setAnEntity: <(Entity *)newAnEntity>];
    }
    return self;
}


//=========================================================== 
//  anEntity 
//=========================================================== 
- (Entity *)anEntity
{
    return [[__anEntity retain] autorelease]; 
}
- (void)setAnEntity:(Entity *)newAnEntity
{
    //NSLog(@"in -setAnEntity:, old value of __anEntity: %@, changed to: %@", __anEntity, newAnEntity);
	
    if (__anEntity != newAnEntity) {
        [__anEntity release];
        __anEntity = [newAnEntity retain];
    }
}


//=========================================================== 
// dealloc
//=========================================================== 
- (void)dealloc
{
    [self setAnEntity:nil];
    [super dealloc];
}

@end

//
//  SomeAction.h
//  inheritance

#import "Action.h"

@interface SomeAction : Action {
}

- (void)doThing;

@end


//
//  SomeAction.m
//  inheritance
#import "SomeAction.h"

@implementation SomeAction

- (void)doThing
{
	NSLog(@"SomeAction -doThing");
}

@end


#import "Entity.h"
#import "SomeAction.h"

int main (int argc, const char * argv[]) {
	Entity *dude = [Entity new];
	SomeAction *foo = [SomeAction new];
	// *foo is an instance of @SomeAction.
	// @SomeAction is a subclass of @Action
	// @Action has ivar __anEntity
	// __anEntity is of type @Entity
	// @Entity has a method -sayPleaseWork
	
	[dude sayPleaseWork];  // works, sayPleaseWork is in @Entity
	[foo doThing];  // works, doThing is in @Action.h

	// how can we call [*bar -sayPleaseWork]?
	Entity *bar = [foo anEntity];
	[bar sayPleaseWork]; // don't works, but compiles.
	
	// at this point we should have logged nslog 3 times
	// "please work"
	// "doThing"
	// "please work" --- this doesn't print :-(
	
	[bar release];
	[foo release];
	[dude release];
    return 0;
}