Advanced Swift 3 - Part 9: Ranges | Ray Wenderlich

Official Tutorials
1

In this video you will learn about the Swift range types in detail and shows how they can be extended without repeating yourself.

This is a companion discussion topic for the original entry at https://www.raywenderlich.com/3810-advanced-swift-3/lessons/9
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@rayfix Hey Ray, great vid as always.

Just wondering about why we need to use IndexDistance and numericCast as opposed to just getting the Int result. (Attempt3).

Thanks

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Hi. Sorry for the late reply. I have been geeking out on WWDC.

So. index(_:offsetBy:) takes an IndexDistance type. You can’t just pass an Int in there. IndexDistance is a SignedInteger and Index is an Int. That is a convenient way to convert between the types. Actually I am not aware of any other way to do it. Do you know of one?

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Attempt 3 can be more concise.

extension RandomAccessCollection where Index == Int {
  var random: Iterator.Element {
    precondition(!isEmpty)
    let index: Int = numericCast(startIndex + (endIndex-startIndex).randomUniform)
    return self[index]
  }
}