IOS Animation not working with my animation block - ios

Question

Im Trying to make a red square move from top of view to a random position at the bottom of the view and the return to the top again at random position.
The app starts with the following code into [super viewLoad]:
[redSquare setCenter:CGPointMake(25,25)];
(with the red square view set 50 x 50, this starts the app with the redsquare in the top left corner).
The first part of the animation works well - the red square animates to a random position to the bottom of the page. But, it then jumps to a random position to the top without animation.
Please help what I'm doing wrong or any other solutions to help with this simple animation.
-(void)moving{
[UIView animateWithDuration:1.0 delay:0.0 options:UIViewAnimationCurveEaseIn animations:^{
int randomx = arc4random() % 295;
[redSquare setCenter:CGPointMake(randomx,435)];
} completion:^(BOOL finished) {
[redSquare setCenter:CGPointMake(redSquare.frame.origin.x,25)];
}];
}

Answer 1

Your completion block simply sets the new position. You aren't animating it back to the top:
Try this, instead
-(void)moving {
[UIView animateWithDuration:1.0 delay:0.0 options:UIViewAnimationCurveEaseIn animations:^{
int randomx = arc4random() % 295;
[redSquare setCenter:CGPointMake(randomx,435)];
} completion:^(BOOL finished) {
[UIViewAnimateWithDuration:1.0 delay:0.0 options:UIViewAnimationCurveEaseIn animations:^{
[redSquare setCenter:CGPointMake(redSquare.frame.origin.x,25)];
} completion: NULL
}];
}
Edited to add
It's true that sublevels can get confusing, but you can make life simple and less indented if you define the blocks separately from the method.
For example, you could rewrite the above as:
-(void)moving {
workBlk_t animationBlock = ^ {
int randomx = arc4random() % 295;
[redSquare setCenter:CGPointMake(randomx,435)];
};
void (^completionBlock)(BOOL finished) = ^{
[UIViewAnimateWithDuration:1.0 delay:0.0 options:UIViewAnimationCurveEaseIn animations:^{
[redSquare setCenter:CGPointMake(redSquare.frame.origin.x,25)];
} completion : NULL
};
[UIView animateWithDuration:1.0
delay:0.0
options:UIViewAnimationCurveEaseIn
animations:animationBlock
completion:completionBlock
}];
}

Answer 2

you should start new animation in completion block for example:
completion:^(BOOL finished) {
[UIView animateWithDuration:1.0 delay:0.0 options:UIViewAnimationCurveEaseIn animations:^{
int randomx = arc4random() % 295;
[redSquare setCenter:CGPointMake(randomx,25)];
} completion:^(BOOL finished) {
}];
}];

Answer 3

This part does exactly what you are describing:
completion:^(BOOL finished) {
[redSquare setCenter:CGPointMake(redSquare.frame.origin.x,25)];
}
I.e. returns the object to the top of the screen after the animiation is completed. This will not be animated, it will happen after the animation is completed, and thus it will be instant.
You need to trigger a new animation after the animation is completed.
To create several nested animation blocks can however become a bit messy, the most clean way is to create another method for animating back and call it when the first animation is completed, like this:
-(void) moveDown{
[UIView animateWithDuration:1.0 delay:0.0 options:UIViewAnimationCurveEaseIn animations:^{
int randomx = arc4random() % 295;
[redSquare setCenter:CGPointMake(randomx,435)];
} completion:^(BOOL finished) {
// First animation completed
[self moveBack];
}];
}
-(void) moveBack{
[UIView animateWithDuration:1.0 delay:0.0 options:UIViewAnimationCurveEaseIn animations:^{
[redSquare setCenter:CGPointMake(redSquare.frame.origin.x,25)];
} completion:^(BOOL finished) {
// Second animation completed
}];
}