“missing type in composite literal” when passing value to struct

Question

I have defined my struct like this this below:

type S_LoginSuccessed struct {
    Code int `json:"code"`
    Data struct {
        User struct {
            Sex   string `json:"sex"`
            IsVip bool   `json:"is_vip"`
            Name  string `json:"name"`
        } `json:"user"`
    } `json:"data"`
    Timestamp int64  `json:"timestamp"`
    Message   string `json:"message"`
}

And I use this to call it:

success_message := S_LoginSuccessed{123, {{"male", true, "123"}}, time.Now().Unix(), "123"}

I expect it to be success, How ever the VSCode give me this error:

missing type in composite literal

Answer 1

If you declare the struct in the way you did (nesting structs without creating new types), using them in literals is convoluted as you need to repeat the struct definition.

You'll be forced to use it like this:

success_message := S_LoginSuccessed{
    Code: 123,
    Timestamp: time.Now().Unix(),
    Message: "123",
    Data: struct {
        User struct {
            Sex   string `json:"sex"`;
            IsVip bool   `json:"is_vip"`;
            Name  string `json:"name"`
        }
    }{User: struct {
        Sex   string
        IsVip bool
        Name  string
    }{Sex: "male", IsVip: true, Name: "123"}},
}

Might be more modular to declare the types like this:

type User struct {
    Sex   string `json:"sex"`
    IsVip bool   `json:"is_vip"`
    Name  string `json:"name"`
}

type Data struct{
    User User `json:"user"`
}

type S_LoginSuccessed struct {
    Code int `json:"code"`
    Data Data `json:"data"`
    Timestamp int64  `json:"timestamp"`
    Message   string `json:"message"`
}

Then use it like this:

success_message := S_LoginSuccessed{
    Code: 123,
    Timestamp: time.Now().Unix(),
    Message: "123",
    Data: Data{ User: User{"male", true, "123"} },
}