How to make iOS callback functions? [duplicate]

Question

I can't figure out how to make a function, that will give information to the parent object, that has done something, so I need your help. Example what I want to make:

1. ViewController class instantiate class BottomView and adds it as it's subview.
2. Make a call on instance of BottomView class to start animate something.
3. After the animation ends, I want to give a sign that the animation has ended to the ViewController class, that it could release/remove an instance BottomView from itself.

I need something like a callback. Could you help please?

Answer 1

You could do something like this

@interface BottomView : UIView

@property (nonatomic, copy) void (^onCompletion)(void);

- (void)start;

@end

@implementation BottomView

- (void)start
{
  [UIView animateWithDuration:0.25f
                   animations:^{
                     // do some animation
                   } completion:^(BOOL finished){
                     if (self.onCompletion) {
                       self.onCompletion();
                     }
                   }];
}

@end

Which you would use like

BottomView *bottomView = [[BottomView alloc] initWithFrame:...];
bottomView.onCompletion = ^{
  [bottomView removeFromSuperview];
  NSLog(@"So something when animation is finished and view is remove");
};
[self.view addSubview:bottomView];
[bottomView start];

Answer 2

1.You can do it with blocks!

You can pass some block to BottomView.

2. Or you can do it with target-action.

you can pass to BottomView selector @selector(myMethod:) as action, and pointer to the view controller as target. And after animation ends use performeSelector: method.

3. Or you can define delegate @protocol and implement methods in your viewController, and add delegate property in BottomView. @property (assign) id delegate;

If you make some animations in your BottomView, you can use UIView method

animateWithDuration:delay:options:animations:completion:

that uses blocks as callbacks

[UIView animateWithDuration:1.0f animations:^{

    }];

update:

in ButtomView.h

@class BottomView;

@protocol BottomViewDelegate <NSObject>

- (void)bottomViewAnimationDone:(BottomView *) bottomView;

@end


@interface BottomView : UIView

@property (nonatomic, assign) id <BottomViewDelegate> delegate;

.....
@end 

in ButtomView.m

- (void)notifyDelegateAboutAnimationDone {
   if ([self.delegate respondsToSelector:@selector(bottomViewAnimationDone:)]) {
      [self.delegate bottomViewAnimationDone:self];
   }
}

and after animation complit you should call [self notifyDelegateAboutAnimationDone];

you should set you ViewController class to confirm to protocol BottomViewDelegate

in MyViewController.h

  @interface MyViewController : UIViewController <BottomViewDelegate>
...
@end

and f.e. in viewDidLoad you should set bottomView.delegate = self;