如何将整数和nill数组转换为字符串？ [关闭]

Question

Let's say I have array with integer and nil elements:

[15698, nil, 13000, 560365, nil]

I want to convert this array to string where each element separated by ,.

[15698, null, 13000, 560365, null]

I tried next code but it return 0 instead of null. How to fix it?

func ConvertIntArrayToString(input []int) string {
    if len(input) == 0 {
        return ""
    }
    estimate := len(input) * 4
    b := make([]byte, 0, estimate)
    for _, n := range input {
        b = strconv.AppendInt(b, int64(n), 10)
        b = append(b, ',')
    }
    b = b[:len(b)-1]
    return string(b)
}

---

Here is how I created array:

type NilInt struct {
    value int
    null  bool
}

func (n *NilInt) Value() interface{} {
    if n.null {
        return nil
    }
    return n.value
}

func NewInt(x int) NilInt {
    return NilInt{x, false}
}

func NewNil() NilInt {
    return NilInt{0, true}
}

var x = []utils.NilInt{utils.NewNil(), utils.NewInt(10), utils.NewNil(), utils.NewInt(5)}]

var result strings.Builder

for _, n := range x {
    if n.Value() == nil {
        result.WriteString("null,")
    } else {
        result.WriteString(??? + ",")
    }
}

fmt.Println(result)

Answer 1

As pointed out in the comments by others, an int slice ([]int) cannot contain nil values because it is illegal to assign nil to a variable of a type whose specified zero value is not nil.

If you need a slice that can hold int values and nils you can use []interface{}. Then, to construct the desired string you can simply marshal such a slice with the encoding/json package.

var a = []interface{}{15698, nil, 13000, 560365, nil}
b, err := json.Marshal(a)
if err != nil {
    panic(err)
}
fmt.Println(string(b))

https://play.golang.com/p/hEjTFIoJlXj