Question

I have an implementation which contains a set of methods which do pretty much the same:

- (NSString *) specialKey{
  [self.mySpecialDictionary valueForKey:@"specialKey"];
}

- (NSString *) anotherKey{
  [self.mySpecialDictionary valueForKey:@"mySpecialKey1"];
}

I can now conveniently use those getters like so:

NSString *foo = [Setting sharedInstance].specialKey;

I guess I should now be able to define my Properties dynamic and make one implementation for all those cases, since the string which I look up in my dictionary will always be the name of the getter. I am pretty sure that this should be do-able in Objective-C, but I have no Idea how to achieve this.

Answer 1

The answer is in your question. Try method forwarding:

- (NSMethodSignature*) methodSignatureForSelector:(SEL)selector
{
    return [mySpecialDictionary methodSignatureForSelector:@selector(valueForKey:)];
}

- (void) forwardInvocation:(NSInvocation *)invocation
{
    NSString* propertyName = NSStringFromSelector(invocation.selector);
    [invocation setSelector:@selector(valueForKey:)];
    [invocation setArgument:&propertyName atIndex:2];
    [invocation invokeWithTarget:mySpecialDictionary];
}

Of course, to get rid of compiler warnings it needs to define every property explicit

@property (nonatomic, readonly) NSString* specialKey;
@property (nonatomic, readonly) NSString* anotherKey;

and provide @dynamic for them.