Swift 字符串（String）操作

目录

1. Swift 字符串创建
2. Swift 字符串拼接
3. Swift 字符串追加
4. Swift 字符串格式化
5. Swift 获取字符串长度
6. Swift 判断字符串是否为空
7. Swift 遍历字符串
8. Swift 字符串操作
9. Swift 判断字符串相等
10. Swift 判断字符串包含另一个字符串
11. Swift 字符串分割
12. Swift 数组拼接字符串
13. Swift 字符串截取
14. Swift 字符串替换
15. Swift 字符串插入
16. Swift 字符串删除某段内容

1. Swift 字符串创建

// 类型推断
let str  = "Hello"
// 指定类型
let str1 : String = "Hello"

2. Swift 字符串拼接

let str1 : String = "Hello"
let str2 = "Hello"
print(str1 + "\n" + str2)
// 结果:
/**
Hello
Hello
*/

3. Swift 字符串追加

var str = "Hello"
str.append(" World")
print(str)
// 结果: Hello World

4. Swift 字符串格式化

let str = String(3)
let str1 = String(5.0)
print(str, str1)
/**
结果:3 5.0
*/

// 格式化
let str = String(format: "第%d课程", 1)
let str1 = String(format: "价格%f", 5.68)
print(str, str1)
// 结果:第1课程 价格5.680000
let str2 = String(format: "价格%.2f", 5.68)
print(str2)
// 结果:价格5.68

5. Swift 获取字符串长度

let str = String(format: "价格%.2f", 5.68)
// 获取长度
print(str.count)
// 结果:6

6. Swift 判断字符串是否为空

let str = "swift"
let str1 = ""
print(str.isEmpty)
// 结果:false
print(str1.isEmpty)
// 结果:true

7. Swift 遍历字符串

let str = "5.68"
for char in str {
    print(char)
    // 结果：
    /**
      5
      .
      6
      8
      */
}

8. Swift 字符串操作

8.1 获取首字符

let str = "this"
print(str[str.startIndex])
// 结果:t

8.2 删除首字符

var str = "ABC"
str.removeFirst()
// 等同于 str.remove(at: str.startIndex)
print(str)
// 结果: BC

8.3 删除指定位置

var str = "ABCDEFGH"
str.remove(at: str.index(str.startIndex, offsetBy: 2))
print(str)
// 结果: ABDEFGH

8.4 删除最后一个字符

var str = "ABC"
str.removeLast()
// 等同于str.remove(at: str.index(str.endIndex, offsetBy: -1))
print(str)
// 结果: AB

8.5 删除所有内容

var str = "ABCDEFGH"
str.removeAll()

8.6 删除头尾指定位数内容

var str = "ABCDEFGH"
str.removeFirst(2)
str.removeLast(2)
print(str)
// 结果:CDEF

9. Swift 判断字符串相等

let str1 : String = "Hello"
let str  = "Hello"
let str2 = "Hello world"

// 需要知道大小
let isSame = str1.compare(str2)
// 枚举 ComparisonResult -1 0 1
print(isSame.rawValue)
// 结果: -1
print(str1.compare(str).rawValue)
// 结果: 0

// 只需要知道内容是否相等
print(str1 == str)
// 结果: true

10. Swift 判断字符串包含另一个字符串

let str  = "Hello"
let str1 = "Hello world"
let rec = str1.contains(str)
print(rec)
// 结果: true

11. Swift 字符串分割

let str = "Hello world"
let arr = str.split(separator: " ")
print(arr)
// 结果: ["Hello", "World"]

12. Swift 数组拼接字符串

let arr = ["Hello", "World"]
let joined = arr.joined()
print(joined)
// 结果: HelloWorld

let sepJoined = arr.joined(separator: "----")
print(sepJoined)
// 结果: Hello----World

13. Swift 字符串截取

// 头部截取
let str = "asdfghjkl;'"
let str1 = str.prefix(2);
print(str1)
// 结果: as
  
// 尾部截取  
let str2 = str.suffix(3);
print(str2)
// 结果: l;'

// range 截取
let index3 = str.index(str.startIndex, offsetBy: 3)
let index4 = str.index(str.startIndex, offsetBy: 5)
let str5 = str[index3...index4]
print(str5)
// 结果:fgh

// 获取指定位置字符串
let range = str.range(of: "jk")!
print(str[str.startIndex..<range.lowerBound])
// 结果:asdfgh
print(str[str.startIndex..<range.upperBound])
// 结果:asdfghjk

14. Swift 字符串替换

// 替换
let str = "all the world"
let str1 = str.replacingOccurrences(of: "all", with: "haha")
print(str1)
// 结果: haha the world

15. Swift 字符串插入

var str = "ABCDEFGH"
// 单个字符
str.insert("X", at:str.index(str.startIndex, offsetBy: 6))
print(str)
// 结果: ABCDEFXGH
// 多个字符
str.insert(contentsOf: "888", at: str.index(before: str.endIndex))
print(str)
// 结果: ABCDEFXG888H

16. Swift 字符串删除某段内容

var str = "ABCDEFGH"
let start = str.index(str.startIndex, offsetBy: 2)
let end = str.index(str.endIndex, offsetBy: -2)
str.removeSubrange(start...end)
print(str)
// 结果: ABH