var str = "Hello, playground"

extension String {
    var stringByDeletingLastCharacter: String {
        return dropLast(self)
    }
}

println(str.stringByDeletingLastCharacter)   // "Hello, playgroun"

一个快速变化的类别:

extension String {
    mutating func removeCharsFromEnd(removeCount:Int)
    {
        let stringLength = count(self)
        let substringIndex = max(0, stringLength - removeCount)
        self = self.substringToIndex(advance(self.startIndex, substringIndex))
    }
}

使用:

var myString = "abcd"
myString.removeCharsFromEnd(2)
println(myString) // "ab"

补充上述代码，我想删除字符串的开头，但在任何地方都找不到引用。以下是我的做法:

var mac = peripheral.identifier.description
let range = mac.startIndex..<mac.endIndex.advancedBy(-50)
mac.removeRange(range)  // trim 17 characters from the beginning
let txPower = peripheral.advertisements.txPower?.description

这将从字符串的开头修剪17个字符(字符串的总长度是67，从末尾向前移动-50，就得到了它。

简单回答(2015-04-16有效):removeAtIndex(mystring . endindex .前任())

例子:

var howToBeHappy = "Practice compassion, attention and gratitude. And smile!!"
howToBeHappy.removeAtIndex(howToBeHappy.endIndex.predecessor())
println(howToBeHappy)
// "Practice compassion, attention and gratitude. And smile!"

元:

语言继续着它的快速进化，使得许多以前很好的sos答案的半衰期变得危险地短暂。学习语言并参考真正的文档总是最好的。

另一种方法如果你想从末尾删除一个或多个字符。

var myStr = "Hello World!"
myStr = (myStr as NSString).substringToIndex((myStr as NSString).length-XX)

其中XX是要删除的字符数。

Swift 3:当你想删除尾随字符串:

func replaceSuffix(_ suffix: String, replacement: String) -> String {
    if hasSuffix(suffix) {
        let sufsize = suffix.count < count ? -suffix.count : 0
        let toIndex = index(endIndex, offsetBy: sufsize)
        return substring(to: toIndex) + replacement
    }
    else
    {
        return self
    }
}