Swift hasSuffix方法崩溃应用程序

Question

我试图检测用户的输入是否以空格结尾，如果是，则删除该空格。我使用.hasSuffix（）方法来查看空间是否存在，它应该返回一个我可以测试的布尔变量并确定正确的操作过程。但是，当我检查值是true还是false时，应用程序崩溃。对于为什么会这样的想法？这是代码：

var userGuess = userGuessField.text.lowercaseString

var guessEndsWithSpace: Bool = userGuess.hasSuffix(" ")

        // The above will return true if the string ends with a space, so when this happens, remove the space and then check their guess

        if (guessEndsWithSpace == true) {

            println("Guess ends with a space")

            // checkAnswer(userGuess)

        } else {

            println("Guess does not end with a space")
            // Otherwise, just check their guess

            // checkAnswer(userGuess)