如何获取字符串的最后4个字符？

Question

我需要分隔一个字符串的最后4个字母.我怎么能分开呢？字符串的长度在变化.

例如:

var a = "StackOverFlow"
var last4 = a.lastFour //That's what I want to do
print(last4) //prints Flow

Answer 1

一个解决方案是 substringFromIndex

let a = "StackOverFlow"
let last4 = a.substringFromIndex(a.endIndex.advancedBy(-4))

或suffix上characters

let last4 = String(a.characters.suffix(4))

代码是Swift 2

斯威夫特3:

在Swift 3中,第一个解决方案的语法已更改为

let last4 = a.substring(from:a.index(a.endIndex, offsetBy: -4))

斯威夫特4:

在Swift 4中它变得更方便:

let last4 = a.suffix(4)

结果的类型是一种新类型Substring,String在许多情况下表现为.但是,如果子串应该离开创建它的范围,则必须创建一个新String实例.

let last4 = String(a.suffix(4))

Answer 2

String substr = a.substring(a.length() - 4)

语法错了.在Swift的vars之前没有类型.

let a = "1234567890"
let last4 = String(a.characters.suffix(4))
print(last4)

适用于Swift 3.0