递归扩展包含指针的结构定义

Question

This question based on following: go reflection deeply in struct I need same thing - expand struct definition to pass it then as JSON object but with only difference that struct contains pointers to another structs. So, provided code unable to handle that. I tried to modify it in following way:

func printFields(prefix string, t reflect.Type) {
    for i := 0; i < t.NumField(); i++ {
        f := t.Field(i)
        fmt.Printf("%v%v %v
", prefix, f.Name, f.Type)
        if f.Type.Kind() == reflect.Struct {
            fmt.Println(reflect.New(f.Type))
            printFields(fmt.Sprintf("  %v", prefix), f.Type)
        } else if f.Type.Kind() == reflect.Ptr {
            fmt.Println("type ", f.Type )
            printFields(fmt.Sprintf("  %v", prefix), f.Type)
        }
    }
}

But it falls to panic in a case of pointers. How to fix that?

EDIT: got what I needed:

func printFields(prefix string, t reflect.Type) {
    if t.Kind() != reflect.Struct {
        return
    }
    for i := 0; i < t.NumField(); i++ {
        f := t.Field(i)
        fmt.Printf("%v%v %v
", prefix, f.Name, f.Type)
        if f.Type.Kind() == reflect.Struct {
            fmt.Println(reflect.New(f.Type))
            printFields(fmt.Sprintf("  %v", prefix), f.Type)
        } else if f.Type.Kind() == reflect.Ptr {
            printFields(fmt.Sprintf("  %v", prefix), f.Type.Elem())
        }
    }
}

func printExpandedStruct(s interface{}) {
    printFields("", reflect.ValueOf(s).Type())
}

Answer 1

If the field type is a pointer, then use the element type of the pointer. Otherwise, the logic is the same as in the linked question.

func printFields(prefix string, t reflect.Type) {
    for i := 0; i < t.NumField(); i++ {
        f := t.Field(i)
        fmt.Printf("%v%v %v
", prefix, f.Name, f.Type)
        ft := f.Type
        if ft.Kind() == reflect.Ptr {
            ft = ft.Elem()
        }
        if ft.Kind() == reflect.Struct {
            printFields(fmt.Sprintf("  %v", prefix), ft)
        }
    }
}

Run it on the playground.

The following code handles the more general case where the fields can be arrays, slices, channels, pointers or combinations of these kinds.

func printFields(prefix string, t reflect.Type) {
    for i := 0; i < t.NumField(); i++ {
        f := t.Field(i)
        fmt.Printf("%v%v %v
", prefix, f.Name, f.Type)
        ft := f.Type
        for ft.Kind() == reflect.Ptr ||
            ft.Kind() == reflect.Slice ||
            ft.Kind() == reflect.Array ||
            ft.Kind() == reflect.Chan {
            ft = ft.Elem()
        }
        if ft.Kind() == reflect.Struct {
            printFields(fmt.Sprintf("  %v", prefix), ft)
        }
    }
}

Run it on the playground.