Swift Array闭合扩展名引发错误

Question

I have an extension on Array instances for looping over with indices in mind like so:

extension Array {
    func fun (_ iterator: (Int, Element) -> Void) -> Void {
        for (key,value) in self.enumerated() {
            iterator(key,value)
        }
    }
}

Now, I want to call it :

[.leading,.trailing,.bottom,.top].fun {
    (index, element) in

    var c : Int = index % 2 == 0 ? 20 : -20 // THAT LINE
    NSLayoutConstraint(item: subView, attribute: element, relatedBy: .equal, toItem: self.view, attribute: element , multiplier: 1, constant: c ).isActive = true
}

However that raises an error: Type of expression is ambiguous without more context. When I remove the line ("THAT LINE" in the snippet) - it works. When I add this or any other code, even some variable declarations - it gives me the same exception.

This error appears ONLY in Xcode, in terminal it works:

🐄  swift
Welcome to Apple Swift version 3.0.2 (swiftlang-800.0.63 clang-800.0.42.1). Type :help for assistance.
  1>  
  2>  
  3> extension Array { 
  4.     func fun (_ iterator: (Int, Element) -> Void) -> Void { 
  5.         for (key,value) in self.enumerated() { 
  6.             iterator(key,value) 
  7.         } 
  8.     } 
  9. }
 10> [0,1,2,3,4].fun { 
 11.     (index, element) in 
 12.  
 13.     var c : Int = index % 2 == 0 ? 20 : -20 // THAT LINE 
 14.     print(c)
 15. } 
20
-20
20
-20
20

Answer 1

Seems like type of array elements issue.

Try [NSLayoutAttribute.leading, NSLayoutAttribute.trailing, NSLayoutAttribute.bottom, NSLayoutAttribute.top] instead of [.leading,.trailing,.bottom,.top] .

And constant: CGFloat(c) instead of constant: c .