Swift 中的 String使用

1.移除一段特定的字符串

 var str = "Hello word!"
 let range = str.index(str.startIndex, offsetBy: 5)..<str.endIndex
 str.removeSubrange(range) 
 print(str)  // 输出：Hello

2.插入一个字符串

 var str = "Hello！"
 str.insert(contentsOf:"world", at: str.index(before: str.endIndex))
 print(str) // Helloworld！ 

3.替换字符串

 //字符串替换 (写在String类扩展里)
  func replace(of: String, with: String) -> String {
    
    
    return self.replacingOccurrences(of: of, with: with)
  }

  let greeting = "Hello,world"
  let str = greeting.replace(of: "world", with: "jesse")
  print(str) //Hello,jesse

4.给String类添加下标脚本，支持索引访问(写在String类扩展里)

 extension String
{
    
    
    subscript(start:Int, length:Int) -> String
        {
    
    
        get{
    
    
            let index1 = self.index(self.startIndex, offsetBy: start)
            let index2 = self.index(index1, offsetBy: length)
            return String(self[index1..<index2])
        }
        set{
    
    
            let tmp = self
            var s = ""
            var e = ""
            for (idx, item) in tmp.enumerated() {
    
    
                if(idx < start)
                {
    
    
                    s += "\(item)"
                }
                if(idx >= start + length)
                {
    
    
                    e += "\(item)"
                }
            }
            self = s + newValue + e
        }
    }
    subscript(index:Int) -> String
        {
    
    
        get{
    
    
            return String(self[self.index(self.startIndex, offsetBy: index)])
        }
        set{
    
    
            let tmp = self
            self = ""
            for (idx, item) in tmp.enumerated() {
    
    
                if idx == index {
    
    
                    self += "\(newValue)"
                }else{
    
    
                    self += "\(item)"
                }
            }
        }
    }
}

使用案例

var greeting = "Hello, world!"
let subStr = greeting[2,3]
print(subStr)//打印结果为：llo
greeting[2,3] = "222"
print(greeting)//打印结果为：He222, world!
print(greeting[3])//打印结果为：2

5.多行字面量：使用三个双引号（"""）包裹

  let str = """
           12345
           234567
           3456789
           """
  print(str)

打印结果

12345
234567
3456789

6.字符串切割（拆分）

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

7.判断字符串是否是整数（写在类扩展中）

  func isPureInt() -> Bool {
    
    
        let scan = Scanner(string: self)
        var val = 0
        let boolValue = scan.scanInt(&val) && scan.isAtEnd
        return boolValue
  }

使用案例

 let str = "Hello，world"
 print(str.isPureInt())  //false
 let str1 = "123"
 print(str1.isPureInt()) //true