drxrgundk062317205
2018-09-03 12:50
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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?

图片转代码服务由CSDN问答提供 功能建议

我要初始化一个包含接口列表的映射,而不必一个个添加它们:

  type像素结构{
 X float64 
 Y float64 
} 
 
type顶点结构{
 X float64 
 Y float64 
 Z float64 
} 
type测试对 struct {
文件名字符串
值[]界面{} 
} 
var测试= map [string] testpair {
“ test1”:{
文件名:“ file1.csv”,
值:[] 像素{
 {X:12.5,Y:23.4},
 {X:17.2,Y:7.9},
} 
},
“ test2”:{
 filename:“ file2.csv”,  
值:[]顶点{
 {X:10.7,Y:13.3,Z:25.1},
 {X:18.3,Y:16.9,Z:16.4},
} 
},
}  
   
 
 

编译器将输出以下错误:

不能使用[]像素文字(典型 e [] Pixel)作为字段值中的[] interface {}类型

如果将[] interface {}切换为[] Pixel,则可以初始化地图 但是我只能用唯一类型的Pixel或Vertex做到这一点。

有没有一种方法可以强制编译器在声明它为接口数组的同时接受具有特定结构的数组初始化?

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4条回答 默认 最新

  • duanao4503 2018-09-03 13:04
    已采纳

    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.

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  • dongmou5628 2018-09-03 12:55

    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.

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  • dongpao5127 2018-09-03 13:21

    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}}}}
    
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  • duanbi7204 2019-02-15 09:39

    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
    
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