douhua9726 2019-04-19 13:02
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从命令行询问两个整数-GOlang [关闭]

I am perfectly fine with asking one integer input from user, but with two, it fails with "no new variables on left side of :=(undefined)"

and i dont see any ideas how to fix it..

i tried to create two variable-s (int type). with one it works perfectly fine, but with adding other one, it wails..

var loop_count int
         fmt.Println("Insert start ID : ")

         _, err1 := fmt.Scanf("%d", &loop_count)

         if err1 != nil {
            fmt.Println(err)
         }

    arr := make([]uint8, loop_count) //How many times it loops

    var url_id int
         fmt.Println("Insert start ID : ") //From where it starts

         _, err := fmt.Scanf("%d", &url_id)

         if err != nil {
            fmt.Println(err)
         }

         fmt.Println("Starting download from : ", url_id)

So i want to ask two things from console:

  1. Loop count (how many times should it loop)
  2. From what ID it should start downloading.
  • 写回答

1条回答 默认 最新

  • douzuizhuo0587 2019-04-19 13:26
    关注

    You get this error because you have already declare "err", when you using ":=" operator you are trying to redeclare(create the variable with the same name) this variable. You should use "=" to change value. And code blow work fine, but you`d better add validation:

    var loop_count int
    fmt.Print("Insert loop_count ID: ")
    
    _, err := fmt.Scanf("%d", &loop_count)
    
    if err != nil {
        fmt.Println(err)
    }
    
    var url_id int
    fmt.Print("
    Insert url_id ID: ") //From where it starts
    
    _, err = fmt.Scanf("%d", &url_id)
    
    if err != nil {
        fmt.Println(err)
    }
    
    fmt.Println("
    Starting download from: ", url_id)
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论

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