Passing class method as selector problem.

Question

Hi,

I want to build a selector from a class method.

I'm doing it this way:

NavigationTreeActionHandler* handler=[NavigationTreeActionHandler self];
NavigationTreeNode* bombsNode=new NavigationTreeNode("Bombs","bigbomb.tif"
     ,handler,@selector(BigBombButtonPressed:));

I need to pass to NavigationTreeNode the target and the selector to the target method. I try to get the target using the self property of the class object (Don't know if htis is the correct way to do it). Then I get the selector for the class method I want to call on the class.

Everything compiles ok but it fails when I use:

[[handler class] instanceMethodSignatureForSelector:selector];

I get a nil and don't really know why... could anybody help please?

Thanks in advance, Olson.

Answer 1

A few suggestions:

• [NavigationTreeActionHandler self] will work fine to get the class object, but I would declare handler as type id instead of NavigationTreeActionHandler*, because it's not a reference to an instance that type

• [handler class] is redundant; handler is already the class object.

• instanceMethodSignatureForSelector: is only going to return nil if handler does not implement the selector. Verify your spelling etc., and try throwing in an NSLog to verify what you're receiving:

  NSLog("handler = %@ sel = %@", handler, NSStringFromSelector(selector));

But I'm unclear on what you're trying to do with instanceMethodSignatureForSelector: in the first place. If you're just trying to call the class method, wouldn't [handler performSelector:selector]; do what you want?

Answer 2

Thanks for the answer.

Well I'm still getting nil... I have been playing a lot with this without any luck. And I'm pretty sure the selector is implemented (see below). Here is the code I'm using:

@interface NavigationTreeActionHandler : NSObject 
{
}
+ (void) BombGroupButtonPressed: (id) obj;
+ (void) BombLittleButtonPressed: (id) obj;
+ (void) BigBombButtonPressed:(id) obj;

@end

//And this is the client code
id handler=[NavigationTreeActionHandler self];

NavigationTreeNode* rootNode=new NavigationTreeNode("Root",0,nil,nil);
//This is what returns 
sig = [handler instanceMethodSignatureForSelector:@selector(BigBombButtonPressed:)];

The [handler instanceMethod... ] is not something I'm using my self, but from a framework (cocos2d), so I must stick to it (Just checking why cocos2d breaks there).

Thanks in advance.