swift4.0 String 格式化

1字符串类型的初始化

  let str = String(format:"hello %@", arguments:["word"])
        print(str)

2 Int 类型的初始化

 let number = 1
        
        let str = String(format: "第%d行", arguments: [number]) // 第一行
       
        let str = String(format: "第%03d行", arguments: [number]) // 第001行

        print(str)

3 Double 类型

let number = 2.22222
          let str = String(format: "第%fkg", arguments: [number])   //2kg
        let str1 = String(format: "第%.0fkg", arguments: [number])   //2kg
        let str1 = String(format: "第%.1fkg", arguments: [number]) //2.2kg