if、switch 语法进一步精简

• 原来

  func test(_ flag: Bool) {
          
      let string: Stirng
      if flag {
          string = "true"
      }
      else {
          string = "false"
      }
      print(string)
  }

  func test(_ flag: Bool) {
          
      let string: Stirng
      switch flag {
          case true:  string = "true"
          case false: string = "false"
      }
      print(string)
  }

• 现在在 Swift 5.9 下

  func test(_ flag: Bool) {
          
      let string = if flag { "true" } else { "false" }
      
      print(string)
  }

  func test(_ flag: Bool) {
          
      let string = switch flag {
          case true:  "true"
          case false: "false"
      }
      
      print(string)
  }