如何在不使用swift数组的情况下获取字符串的最后一个字符？

Question

我有一个字符串

let stringPlusString = TextBoxCal.text

我想得到stringPlusString的最后一个字符我不想在java上使用数组charAt但我在swift上找不到这个关键字

Answer 1

使用last获取最后Character

Swift 4 ：

let str = "hello world"
let lastChar = str.last!   // lastChar is ""

Swift 2 和 Swift 3 ：

let str = "hello world"
let lastChar = str.characters.last!   // lastChar is ""

Swift 1.2 ：

let str = "hello world"
let lastChar = last(str)!   // lastChar is ""

订阅String以获取最后Character

适用于 Swift 3 和 Swift 4 ：

let str = "hello world"
let lastChar = str[str.index(before: str.endIndex)]   // lastChar is ""

Swift 1.2 和 Swift 2 ：

let str = "hello world"
let lastChar = str[str.endIndex.predecessor()]   // lastChar is ""

Answer 2

“没有在swift上使用Array”

你走了：

var text = "Lorem ipsum"
var lastChar = text.substringFromIndex(text.endIndex.predecessor())

Answer 3

斯威夫特4：

首先是一些char 最后一些char

let strOSName = "mac operating system"
print(strOSName.prefix(3))       //first char. o/p:  MAC
print(strOSName.suffix(6))       //last char.  o/p:  system

Answer 4

    let text = "Muhammad Raza"
    println("\(text[advance(text.endIndex, -1)])")

简而言之！

Answer 5

这是另一种从字符串中获取最后一个字母的简短方法：

let text = "some string"
last(text) // returns {Some "a"}

方法last（）返回一个可选的Character。

Answer 6

详细信息

• Swift 5.1，Xcode 11.2.1

解决方案

extension String {
    func onlyLastCharacters(_ count: Int) -> String { return String(suffix(count)) }
    func onlyLastCharacters(_ count: Int, checkLength: Bool) -> String? {
        if checkLength {
            if self.count >= count { return onlyLastCharacters(count) }
            return nil
        }
        return String(suffix(count))
    }
}

用法

str.onlyLastCharacters(6)
str.onlyLastCharacters(13, checkLength: true)

完整样本

  

别忘了在此处粘贴解决方案代码

var testNumber = 0
func show(original: String, modified: String?) {
    testNumber += 1
    if let string = modified {
        print("\(testNumber). Original: \"\(original)\", modified: \"\(string)\"")
    } else {
        print("\(testNumber). nil | count: nil")
    }
}

var str = "Hello world!"
show(original: str, modified: str.onlyLastCharacters(6))
show(original: str, modified: str.onlyLastCharacters(12))
show(original: str, modified: str.onlyLastCharacters(13, checkLength: false))
show(original: str, modified: str.onlyLastCharacters(13, checkLength: true))

str = ""
show(original: str, modified: str.onlyLastCharacters(10))
show(original: str, modified: str.onlyLastCharacters(10, checkLength: true))
show(original: str, modified: str.onlyLastCharacters(10, checkLength: false))

日志

1. Original: "Hello world!", modified: "world!"
2. Original: "Hello world!", modified: "Hello world!"
3. Original: "Hello world!", modified: "Hello world!"
4. nil | count: nil
5. Original: "", modified: ""
6. nil | count: nil
7. Original: "", modified: ""