Question

When programming for iOS, I frequently find myself faced with the following situation:

- (void)someMethod
{
    [self performSomeAnimation];

    //below is an action I want to perform, but I want to perform it AFTER the animation
    [self someAction];
}

- (void)performSomeAnimation
{
    [UIView animateWithDuration:.5 animations:^
    {
        //some animation here
    }];
}

Faced with this situation, I usually end up just copy/pasting my animation code so that I can use the completion block handler, like so:

- (void)someMethod
{
    [self performSomeAnimation];


    //copy pasted animation... bleh
    [UIView animateWithDuration:.5 animations:^
    {
        //same animation here... code duplication, bad.
    }
    completion^(BOOL finished)
    {
        [self someAction];
    }];
}

- (void)performSomeAnimation
{
    [UIView animateWithDuration:.5 animations:^
    {
        //some animation here
    }];
}

What is the proper way to solve this problem? Should I be passing a block of code to my -(void)performSomeAction method, like below, and executing that block on completion of the animation?

- (void)someMethod
{
    block_t animationCompletionBlock^{
        [self someAction];
    };

    [self performSomeAnimation:animationCompletionBlock];
}

- (void)performSomeAnimation:(block_t)animationCompletionBlock
{
    [UIView animateWithDuration:.5 animations:^
    {
        //some animation here
    }
    completion^(BOOL finished)
    {
        animationCompletionBlock();
    }];
}

Is that the proper way to solve this problem? I guess I have been avoiding it because I’m not THAT familiar with block usage (not even sure if I declared that block properly) and it seems like a complicated solution to a simple problem.

Answer 1

You could also do this:

- (void)performSomeAnimationWithCompletion:(void(^)(void))animationCompletionBlock
{
    [UIView animateWithDuration:.5 animations:^
    {
        //some animation here
    }
    completion^(BOOL finished)
    {
        animationCompletionBlock();
    }];
}

And instead of explicitly defining a block and passing it as parameter, you can call it directly like this (this is how block animations work for UIView, for example):

- (void)someMethod
{
    [self performSomeAnimationWithCompletion:^{

        [self someAction];

    }];
}