使用 Go 实例化一个新 obj 反射并键入 assert 到接口

Question

I can't explain why the following is working.

package main

import (
    "fmt"
    "reflect"
    "strings"
)

type MyInterface interface {
    someFunc()
}

type Dock struct {
}

func (d *Dock) someFunc() {
}

type Group struct {
    Docks []Dock `better:"sometag"`
}

func foo(model interface{}) {
    v1 := reflect.Indirect(reflect.ValueOf(model))
    for i := 0; i < v1.NumField(); i++ {
        tag := v1.Type().Field(i).Tag.Get("better")
        if strings.HasPrefix(tag, "sometag") {
            inter := v1.Field(i).Interface()
            typ := reflect.TypeOf(inter).Elem()
            fmt.Println("Type:", typ.String())

            // Want to instantiate type like &Dock{} then assign it to some interface,
            // but using reflect
            n := reflect.New(typ)
            _, ok := n.Interface().(MyInterface)            
            fmt.Println("Why is it OK?", ok)

        }
    }
}

func main() {
    g := &Group{}
    foo(g)

    /*var v1, v2 interface{}
    d1 := &Dock{}
    v1 = d1
    _, ok1 := v1.(MyInterface)

    d2 := Dock{}
    v2 = d2
    _, ok2 := v2.(MyInterface)
    fmt.Println(ok1, ok2)*/
}

It prints

Type: main.Dock
OK? true

If it's a Dock type, then it's not a pointer to Dock. Why does it conforms to MyInterface ?

https://play.golang.org/p/Z9mR8amYOM7

Where as the d2 example in the comment does not.

Answer 1

In go doc for reflect.New

New returns a Value representing a pointer to a new zero value for the specified type. That is, the returned Value's Type is PtrTo(typ).

n := reflect.New(typ)
fmt.Println("Type:", n.String())

It will print Type: <*main.Dock Value> means n is a pointer of Dock .You miss the part using reflect.New return the pointer.