drxrgundk062317205 2018-09-03 12:50
浏览 653
已采纳

如何在Golang中初始化接口数组?

I want to initialize a map containing a list of interface without having to add them one by one:

type Pixel struct {
    X float64
    Y float64
}

type Vertex struct {
    X float64
    Y float64
    Z float64
}
type testpair struct {
    filename       string
    values     []interface{}
}
var tests = map[string]testpair{
   "test1": {
               filename: "file1.csv",
               values:  []Pixel{
                           {X: 12.5, Y: 23.4},
                           {X: 17.2, Y: 7.9},
                      }
            },
   "test2": {
               filename: "file2.csv",
               values:  []Vertex{
                           {X: 10.7, Y: 13.3, Z: 25.1},
                           {X: 18.3, Y: 16.9, Z: 16.4},
                      }
            }, 
}

The compiler would output such an error:

cannot use []Pixel literal (type []Pixel) as type []interface {} in field value

If I switch []interface{} to []Pixel, I can initialize the map but I can do it only with a unique type Pixel or Vertex.

Is there a way to force the compiler to accept array initialization with a specific struct while declaring it as an array of interface?

  • 写回答

4条回答 默认 最新

  • duanao4503 2018-09-03 13:04
    关注

    If you have to create a slice of values for passing to something that requires a slice of interface{} (which, depending on the context, may or may not be appropriate design) or a slice of any more specific interface, you have to specify each element fully, like this:

    []interface{}{ 
        Pixel{X: 12.5, Y: 23.4},
        Pixel{X: 17.2, Y: 7.9},
    }
    

    That also means that you can pass things like:

    []interface{}{
        Pixel{X: 12.5, Y: 23.4},
        Vertex{X: 10.7, Y: 13.3, Z: 25.1},
    }
    

    which is hardly something you intended, and compiler won't warn you. I don't see that a big deal for the testing code, though.

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论
  • dongmou5628 2018-09-03 12:55
    关注

    Is there a way to force the compiler to accept array initialization with a specific struct while declaring it as an array of interface?

    No. Basically you cannot force the Go compiler to anything.

    See also the FAQ: https://golang.org/doc/faq#convert_slice_of_interface

    You must supply a []interface{}.

    But please stop doing this and come up with something not requiring the empty interface.

    评论
  • dongpao5127 2018-09-03 13:21
    关注

    To be able to initialize you need to input a type to the interface and not an array of type, so suggest you to change as follow:

        type Pixel struct {
        X float64
        Y float64
    }
    type Pixels []Pixel
    
    type Vertex struct {
        X float64
        Y float64
        Z float64
    }
    type Vertexs []Vertex
    type testpair struct {
        filename string
        values   interface{}
    }
    var tests = map[string]testpair{
        "test1": {
            filename: "file1.csv",
            values: Pixels{
                Pixel{X: 12.5, Y: 23.4},
                Pixel{X: 17.2, Y: 7.9}}},
        "test2": {
            filename: "file2.csv",
            values: Vertexs{
                Vertex{X: 10.7, Y: 13.3, Z: 25.1},
                Vertex{X: 18.3, Y: 16.9, Z: 16.4}}}}
    
    评论
  • duanbi7204 2019-02-15 09:39
    关注

    I had the same problem but was about to use primitives so this suggested solution here want work. In that case I helped my self out with:

    args := make([]interface{}, 2)
    args[0] = "some string"
    args[1] = 1 //some int
    
    评论
查看更多回答(3条)

报告相同问题?

悬赏问题

  • ¥15 控制面板卸载无权限!!
  • ¥20 vb调用dll报错找不到文件
  • ¥20 SQL如何做交集查询
  • ¥15 unity 绘画方面的问题
  • ¥15 FTP 明明给了权限但是还是550 Permission denied问题
  • ¥20 Java的kafka错误unknowHostException
  • ¥20 gbase 8a没有lisense,需要获取一个lisense
  • ¥15 前端的3d饼图不知道用啥框架做的
  • ¥15 算法问题 斐波那契数 解答
  • ¥15 VS2019 SPY++ 获取句柄操作