CGPoint center animation "nullified" by CGAffineTransform - objective-c

Question

i'm new to Objective-C and Xcode... I'm following a tutorial that explain how to move a car(a ImageView) to the top of the screen, rotate it, an then back to the bottom of the display.
This is the code:
- (IBAction)testDrive:(id)sender {
CGPoint center = CGPointMake(_car.center.x, self.view.bounds.origin.y + _car.bounds.size.height/2 +100);
[UIView animateWithDuration:3
animations:^ { _car.center = center;}
completion:^(BOOL finished){[self rotate];}];
}
- (void) rotate{
CGAffineTransform transform = CGAffineTransformMakeRotation(M_PI);
void (^animation)() = ^() { _car.transform = transform;
};
void (^completion)(BOOL) = ^(BOOL finished){
[self returnCar];
};
[UIView animateWithDuration:3 animations:animation completion:completion];
}
The problem is that the car moves to the top, but then it's position is resetted at the bottom of the screen, like the center was resetted to the default center value, and only then is rotated.. I can't find a solution, need your help!

Answer 1

When you do an animation, its effects are temporary, and by default they don't actually mutate your layers/views. Typically, you would explicitly write the "end" values into the layers/views in the completion block. You will need to do this for each animation in your "chain" of animations. With your code, I suspect you'd get the desired outcome if you did this:
- (IBAction)testDrive:(id)sender {
CGPoint center = CGPointMake(_car.center.x, self.view.bounds.origin.y + _car.bounds.size.height/2 +100);
[UIView animateWithDuration:3
animations:^ { _car.center = center;}
completion:^(BOOL finished){ _car.center = center; [self rotate];}];
}
- (void) rotate{
CGAffineTransform transform = CGAffineTransformMakeRotation(M_PI);
void (^animation)() = ^() { _car.transform = transform;
};
void (^completion)(BOOL) = ^(BOOL finished){
_car.transform = transform;
[self returnCar];
};
[UIView animateWithDuration:3 animations:animation completion:completion];
}
You'll also want to make a corresponding change in -returnCar.
The idea here is that the animation effects only the "presentation layer" but not the "model layer." If you want the model layer to reflect the "after" state of the animation, you need to explicitly do that.

Answer 2

After smashing my head for hours i found the solution to this problem, that was due to AutoLayout.
This is the working code
self.topConstraint.constant = self.topConstraint.constant-self.topConstraint.constant;
[self.car setNeedsUpdateConstraints]; // 2
[UIView animateWithDuration:3
animations:^{
[self.car layoutIfNeeded]; // 3
}
completion:^(BOOL finished){[self rotate]; }
];
Thanks