Swift UIView.animateWithDuration和循环

Question

I have a group of UIImageViews that are stored in an array. I want to animate a certain amount of these ImageViews in the same way. Thus, I have been trying to use the following code:

var lowerViews: [UIImageView] = [imageView1, imageView2, imageView3, imageView4]

var startingIndex = 1;

UIView.animateWithDuration(0.3, delay: 0.1, options: UIViewAnimationOptions.CurveEaseInOut, animations: {

     for index in startingIndex..< lowerViews.count {
         lowerViews[index].frame.origin.y += 100
     }

}, completion: nil)

However at this line:

for index in startingIndex..< lowerViews.count {

Xcode gives me the error:

Expected '{' to start the body of each for-loop

However, I don't believe that this is really the issue. This seems to me that it is an arbitrary syntax error that Xcode gets because I am using the for-loop inside the 'animation' parameter. Since I am still learning a lot about Swift I do not know why this wouldn't work, and so if this assumption is correct, I would like to know why and how I can get around this.

If this is not the case, please let me know, because either way I need to get around the problem.

Thanks in advance

Answer 1

This is a tricky error (note spaces around ..< ).

for index in startingIndex ..< lowerViews.count {

will work or

for index in startingIndex..<lowerViews.count {

will work but:

for index in startingIndex..< lowerViews.count {

won't work.

The reason for this is the fact that when startingIndex..< is used, then ..< is considered to be a postfix (unary) operator (not an infix operator). Therefore the whole expression stops making sense and you start getting strange errors.

Also see what are the rules for spaces in swift