I have not yet been able to figure out how to get a substring of a String in Swift: var str = “Hello, playground” func test(str: String) -> String { return str.substringWithRange( /* What goes here? */ ) } test (str) I'm not able to create a Range in Swift. Autocomplete in the Playground isn’t super helpful - this is what it suggests: return str.substringWithRange(aRange: Range<String.Index>) I ha
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