SWIFT 2.0/3.0 in Xcode 8 beta 5
simple:
let myString = "full text container" myString[myString.startIndex..<myString.startIndex.advancedBy(3)] // prints: ful swift 3.0 in Xcode 8 beta 6 or later
myString[myString.startIndex..<myString.index(myString.startIndex, offsetBy: 3)] // prints: ful