如何在Interface Builder中使用自定义UIButton类别？

Question

I'm coding a simple card game for my younger sister on a whim. I'm using UIButtons: default state is face down, selected state is face up. I need the buttons to have a boolean property that tells me if they've ever been flipped over. If not, it gets set to true (that way I'm not just drawing random cards on each flip). I tried creating a category of UIButton called CardGameButton. In the .h file:

@interface UIButton (CardGameButton)
@property (nonatomic) BOOL discovered;
@end

In the .m file:

@implementation UIButton (CardGameButton)
@dynamic discovered;
@end

This is really all I need. How do I use this in IB? I have a bunch of UIButtons on a screen that I want to be CardGameButtons. But when I try to switch my calls to UIButton in my view controller to CardGameButton, it tells me CardGameButton isn't a type (yes I imported the file). And when I try to switch the class of the UIButtons in the storyboard to CardGameButtons, the console tells me that they're an "unknown class". I tried subclassing UIButton, but that didn't work (I just need them to be RoundedRectButtons with the extra property, and since you can't subclass RoundedRectButton they wouldn't display properly). How do I make this work in IB?

Answer 1

You're treating CardGameButtons as though it's a subclass of UIButton when instead it's a category. Anything you declare as UIButton will have the discovered property as standard, but you can't 'create' a CardGameButtons as it's not a thing in itself.

Answer 2

Categories are not types. They're just used to add some extended behavior to the class.

I suggest that you try subclassing UIButton and call it CardGameButton . Add the BOOL property to its interface. You can still make it a round rect button, by setting buttonType to UIButtonTypeRoundedRect "round rect buttons aren't a separate subclass." . Then override

- (void)sendAction:(SEL)action to:(id)target forEvent:(UIEvent *)event {
    if(event.type == UIEventTypeTouches){
        self.discovered = YES; // or handle the logic as you want here
    }
    [super sendAction:action to:target forEvent:event];
}

You can add a UIButton to your view from the IB, and then its class to your created subclass and set its type to round rect.

---

Edit : As you stated, buttonType is actually readOnly , so we can't use that to draw a round rect button. However, it turns out that it's not hard to draw it.

Check this tutorial . It shows how to do it using CALayer property of UIButton and using UIBezeirPath .