I'm making a calculator app in Swift, once my answer is obtained I want to display it in a UILabel. Only problem is I want to limit said answer to 8 characters. Here is my code:
let answerString = "\(answer)" println(answer) calculatorDisplay.text = answerString.substringToIndex(advance(answerString.startIndex, 8)) This does not return any compiler errors but at runtime I get:
fatal error: can not increment endIndex Any and all help would be greatly appreciated.
There are two different advance() functions:
/// Return the result of advancing `start` by `n` positions. ... func advance<T : ForwardIndexType>(start: T, n: T.Distance) -> T /// Return the result of advancing start by `n` positions, or until it /// equals `end`. ... func advance<T : ForwardIndexType>(start: T, n: T.Distance, end: T) -> T Using the second one you can ensure that the result is within the valid bounds of the string:
let truncatedText = answerString.substringToIndex(advance(answerString.startIndex, 8, answerString.endIndex)) Update for Swift 2/Xcode 7:
let truncatedText = answerString.substringToIndex(answerString.startIndex.advancedBy(8, limit: answerString.endIndex)) But a simpler solution is
let truncatedText = String(answerString.characters.prefix(8)) Update for Swift 3/Xcode 8 beta 6: As of Swift 3, "collections move their index", the corresponding code is now
let to = answerString.index(answerString.startIndex, offsetBy: 8, limitedBy: answerString.endIndex) let truncatedText = answerString.substring(to: to ?? answerString.endIndex) The simpler solution
let truncatedText = String(answerString.characters.prefix(8)) still works.
