How to access a method by inheritance of #protocols in Objective-C? - objective-c

Question

I have a program where inheritance of protocols are there say:
#protocol A
-(void)methodA
#end
The protocol which inherits:
#protocol B<A>
-(void)methodB
#end
The class which implements #protocolA method is
#interface classB<B>
#end
#implementation classB
-(void)methodA
{
//somecode
}
#end
Now i wanted the methodA to be called from Some other class:
#implementation SomeotherClass
{
//call of methodA
//????
id<A>obj=[[classB alloc]init];//i have tried it
[obj methodA];// even this is not working
}
How to do that?

Answer 1

Just send the message as usual:
SomeotherClass *obj = [[[SomeotherClass alloc] init] autorelease];
[obj methodA];
Since instances of classB implement protocol B, they also claim to respond to -methodA.
The following compiles and runs without any problems:
MyClass.h:
#import <Foundation/Foundation.h>
#protocol A
-(void) methodA;
#end
#protocol B <A>
-(void) methodB;
#end
#interface MyClass : NSObject <B>
{
}
#end
MyClass.m:
#import "MyClass.h"
#implementation MyClass
-(void) methodA
{
NSLog(#"%s", __PRETTY_FUNCTION__);
}
-(void) methodB
{
NSLog(#"%s", __PRETTY_FUNCTION__);
}
#end
the code:
MyClass *obj = [[MyClass alloc] init];
[obj methodA];
[obj methodB];
[obj release];

Answer 2

You don't say how it fails to work. I would guess that there's a compilation error as you don't implement methodB in your classB.
Another possibility: what happens after you've initialised classB in SomeOtherClass? Are you sure that you get a valid object back? If it returned a nil the run time would be perfectly within its rights to do nothing when you sent the methodA message to it.