I found strange to force user to write Before invoking a delegation method, make sure the delegate implements it by sending it a respondsToSelector: message. Cocoa Fundamentals Guide (TP40002974 6.0.0) - (void)someMethod { if ( [delegate respondsToSelector:@selector(operationShouldProceed)] ){ if ( [delegate operationShouldProceed] ) { // do something appropriate } } } I'm reading also on bindings (could be like valueHolder) and targetAction. I think that I will have to read that several times :) https://developer.apple.com/legacy/library/documentation/Cocoa/Conceptual/Co... Stef Cocoa Fundamentals Guide (TP40002974 6.0.0) On 16/7/14 10:48, stepharo wrote:
Hi
In the quest for a better UI framework :), I was re rereading about delegate in Cocoa. A delegating object will delegate certain operations to a delegate object (check the attachment). Now I was wondering why this is not a simple delegation they wrote:
The delegating object sends a message only if the delegate implements the method. It makes this discovery by invoking the NSObject method respondsToSelector: in the delegate first.
Cocoa Fundamentals Guide (TP40002974 6.0.0)