Re: How to adopt a superclass's protocol?

FROM : K. Darcy Otto
DATE : Tue Apr 29 22:40:43 2008

The casting worked, and the protocol gets found; but I'm still getting 
a warning that the protocol is not found.  Here's what I have:

Superclass.h:

@protocol Check;

Superclass.m:

@protocol Check

@optional
-(BOOL)optionalMethodToImplement;

@end

(I'm relegating the protocol to the .m file to make it "private" in a 
sense.)

Subclass.h

@interface Subclass : Superclass <Check>

...

Now, the compiler issues a warning at the @interface line in 
Subclass.h - "no definition of protocol 'Check' is found".  But it is 
clear that the protocol is being located at runtime nevertheless, 
because if I eliminate <Check> from the @interface line, 
optionalMethodToImplement: does not get called.  Also, what is 
interesting is that if I move @protocol Check ... @end in Superclass.m 
to Superclass.h, the warning goes away.  So, is there a way to keep 
@protocol Check ... @end in Superclass.m and eliminate the warning?

Thanks.

On 28-Apr-08, at 11:25 PM, Michael Vannorsdel wrote:

> You can make the superclass's method look like this:
>
> - (void)doSomething
> {
>     if([self conformsToProtocol:@protocol(Check)])
>         [(SuperClass <Check> *)self optionalMethodToImplement];
> }
>
> The cast eliminates the compiler warning.
>
> As far as making it private it depends what you mean by that.  If 
> you don't want it visible in headers you're going to distribute you 
> can put:
>
> @protocol Check;
>
> in the public header then actually define the whole protocol in a 
> private undistributed header.
>
>
> On Apr 28, 2008, at 9:22 PM, K. Darcy Otto wrote:
>

>> Okay, I have done this, and things are compiling and running 
>> correctly.  Thank you.  Two additional questions then.  First, I 
>> still get the warning that the superclass "may not respond" to the 
>> method (and to be sure, it is only implemented in the subclass, but 
>> the superclass calls it after a conformsToProtocol: check). 
>> Second, I would like the optionalMethodToImplement to be private - 
>> usually I put this in the .m file under a category; but when I do 
>> that with the protocol, the subclass cannot locate the protocol. 
>> Any suggestions?

>
> _______________________________________________
>
> Cocoa-dev mailing list (<email_removed>)
>
> Please do not post admin requests or moderator comments to the list.
> Contact the moderators at cocoa-dev-admins(at)lists.apple.com
>
> Help/Unsubscribe/Update your Subscription:
> http://lists.apple.com/mailman/options/cocoa-dev/<email_removed>
>
> This email sent to <email_removed>