Sending message to object using selector and NSSelectorFromString - ios

Question

The following will pass the respondsToSelector test, but SIGABRT on the actual call to [viewController selector] or [viewController action:selector]. The stack trace states 'NSInvalidArgumentException, reason: -[MyViewController selector]: unrecognized selector'.
[viewController #selector(selector)] will cause a compile error (error: expected ':' before 'selector').
When the selector is hard coded, all works well.
How do I send a message to an object through a selector?
-(void) notifyViewControllers:(NSString*) message
{
if(!message) return;
SEL selector = NSSelectorFromString(message);
if(!selector) return;
NSArray* viewControllers = [self.tabBarController viewControllers];
if(!viewControllers) return;
for (UIViewController* viewController in viewControllers)
{
if(!viewController) continue;
if ([viewController respondsToSelector:selector]) {
// [viewController selector];
[viewController action:selector];
}
}
}

Answer 1

[self performSelector:#selector(notifyViewControllers:) withObject: message];

Answer 2

Try
[viewController performSelector:selector];
Also check other methods NSObject in performSelector 'family' - with them you can easily call selector with delay and/or on background thread.

Answer 3

Could be useful to know how to do this where you cannot use performSelector, maybe because the selector string must be used within a protocol method:
In order to allow the selector supporting parameters, it should be specified as follow:
NSString *stringForSelector = #"doSomethingAwesome:"; // notice the colon
Let's say we're going to handle a tap gesture
UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:NSSelectorFromString(stringForSelector)];
UIGestureRecognizer class allow to use the recognizer itself in the action callback:
- (void)handleGesture:(UIGestureRecognizer *)gestureRecognizer;
So to do something awesome on Tap, we could write:
- (void)doSomethingAwesome:(UITapGestureRecognizer *)tapGesture
{
// gesture handling with UIGestureRecognizer availability
}