import UIKit

var str1 = "Hello, playground"
str1.removeLast()
print(str1)

var str2 = "Hello, playground"
str2.removeLast(3)
print(str2)

var str3 = "Hello, playground"
str3.removeFirst(2)
print(str3)

Output:-
Hello, playgroun
Hello, playgro
llo, playground

这是一个字符串扩展表单:

extension String {

    func removeCharsFromEnd(count_:Int) -> String {
        let stringLength = count(self)

        let substringIndex = (stringLength < count_) ? 0 : stringLength - count_

        return self.substringToIndex(advance(self.startIndex, substringIndex))
    }
}

对于Swift 1.2之前的版本:

...
let stringLength = countElements(self)
...

用法:

var str_1 = "Maxim"
println("output: \(str_1.removeCharsFromEnd(1))") // "Maxi"
println("output: \(str_1.removeCharsFromEnd(3))") // "Ma"
println("output: \(str_1.removeCharsFromEnd(8))") // ""

参考:

扩展向现有的类、结构或枚举类型添加新功能。这包括扩展您无法访问原始源代码的类型的能力(称为回溯建模)。扩展类似于Objective-C中的类别。(与Objective-C类别不同，Swift扩展没有名称。)

看文档

使用新的Substring类型用法:

斯威夫特4:

var before: String = "Hello world!"
var lastCharIndex: Int = before.endIndex
var after:String = String(before[..<lastCharIndex])
print(after) // Hello world

短:

var before: String = "Hello world!"
after = String(before[..<before.endIndex])
print(after) // Hello world

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。

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。

var str = "Hello, playground"

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

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