Generic NSMenuItem/NSControl validation method, so you can implement a separate -validate<Action>: method for each action

gistfile1.m

//This validation method is completely generic; it dispatches to validate<Action>:, where <Action> is the item's action, duly initially-capitalized.
- (BOOL) validateUserInterfaceItem:(id <NSValidatedUserInterfaceItem>)item {
	SEL action = [item action];
	if (![self respondsToSelector:action]) {
		//We don't respond to the action, so unconditionally return NO.
		return NO;
	}

	/*Determine the selector of the message to send ourselves for actual validation.
	 */
	NSString *actionString = NSStringFromSelector(action);
	NSString *firstCharacter = [actionString substringToIndex:1];
	NSString *andTheRest = [actionString substringFromIndex:1];
	NSString *validationSelectorString = [NSString stringWithFormat:@"validate%@%@",
		[firstCharacter uppercaseString],
		andTheRest
	];
	if (![validationSelectorString hasSuffix:@":"])
		validationSelectorString = [validationSelectorString stringByAppendingString:@":"];
	SEL validationSelector = NSSelectorFromString(validationSelectorString);
	if ([self respondsToSelector:validationSelector])
		return (BOOL)objc_msgSend(self, validationSelector, item);

	//Well, we do respond to the action, so default to YES.
	return YES;
}