Re: selector comparision

On 4 May, 2011, at 0:03, Daniel Luis dos Santos wrote:

> Hello, 
> 
> I am following the apple docs on how to enable menu items according to state in my application :
> The doc is at : http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/MenuList/Articles/EnablingMenuItems.html%23//apple_ref/doc/uid/20000261-BAJBFGED
> 
> I am trying to do something similar to the example code of the method 
> 
> 	- (BOOL)validateUserInterfaceItem:(id <NSValidatedUserInterfaceItem>)anItem
> 
> but in python. The class that holds the actions to the menu items has that method implemented as the docs indicate.
> To avoid hardcoding the methodNames in the code I want to compare the result of the action() method to the selector of each method. My code is :
> 
> 	def validateUserInterfaceItem_(self, anItem):
> 		
> 		theAction = anItem.action()
> 		if (theAction == self.saveAction_):
> 			return NO
> 		return YES

I'm not sure if this is worth the effort, you're still duplicating names. The only (small) advantage is that you don't have to use the Objective-C name. A disadvantage of your code is that 'self.saveAction_' creates a bound selector object, which means this code is less efficient that just using the selector name (although the difference is insignificant here).

Anyway, the code above is broken: "theAction" is a selector name (a byte string), while self.saveAction_ is a bound selector object. You should compare to self.saveAction_.selector instead.

> 
> Somewhere in the same class I have the method :
> 
> 	@IBAction
> 	def saveAction_(self, sender):
> 		... rest of method definition
> 
> To have the selector defined for the above method I also put immediately after the method declaration :
> 
> 	saveAction_ = objc.selector(saveAction_, signature="v@:@")

That's not necessary, @IBAction already does this for you.

> 
> The problem is that the comparison of the result of anItem.action() does not equals the selector for the method.
> If I print both to the terminal using :
> 
> 		print theAction
> 		print self.saveAction_
> 
> I get  :
> 
> 		saveAction:
> 		<selector saveAction: of <menubaractions: 0x1010ee000>>
> 
> The output does not match. It seems like the representation is different. How do I compare both these values successfully ?

Your comparing a selector object with a passed in selector name. To compare you should use self.saveAction_.selector,  that attribute contains the selector name.

Ronald

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