Question

Is it possible to forward a property?

Let’s say I have a proxy class that has a member which has in turns a property called string.

I want my proxy class to have the same property also named string. From there, I would like that whenever I call the getter/setter on the proxy, it set/get value on its class member.

the closest I have come to it is to implement -forwardingTargetForSelector and switch the target when needed but it’s not clean nor pratical (it gives warning and you cannot use the dot-syntax)

Answer 1

You can declare the properties as @dynamic and implement these two methods to handle the forwarding – methodSignatureForSelector: and forwardInvocation:. Implementation will be something has described below –

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {
    if ( alpha && [alpha respondsToSelector:aSelector] ) {
        return [alpha methodSignatureForSelector:aSelector];
    } else {
        return [super methodSignatureForSelector:aSelector];
    }
}

- (void)forwardInvocation:(NSInvocation *)anInvocation {
    if ( alpha && [alpha respondsToSelector:[anInvocation selector]] ) {
        [anInvocation invokeWithTarget:alpha];
    } else {
        [super forwardInvocation:anInvocation];
    }
}