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Mutability warnings

Available from Swift 2.0

Paul Hudson      @twostraws

This is a simple change that is going to go a long way to help code readability. As you know, Swift developers prefer declaring things as constants (using let) rather than variables (using var). But what if you made something a variable by accident? Or if you thought you might need to change it, then never do?

As of Xcode 7 and Swift 2, you'll get warnings in your code whenever you declare variables that never change – Xcode literally examines the way you use the variable and knows if you never change it.

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Other changes in Swift 2.0…

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