如何在Go中找到接口的根实现？

Question

I have an interface RootInterface embedded in a struct OneConcrete. This concrete implementation of the interface is then embedded into another struct TwoConcrete as RootInterface again.

How do I determine that the actual implementation of RootInterface is OneConcrete? The following code hopefully shows what I am trying to achieve:

http://play.golang.org/p/YrwDRwQzDc

package main

import "fmt"

type RootInterface interface {
    GetInt() int
}

type OneConcrete struct {
}

func (oc OneConcrete) GetInt() int {
    return 1
}

type TwoConcrete struct {
    RootInterface
}

func main() {
    one := OneConcrete{}
    fmt.Println("One", one.GetInt())

    two := RootInterface(TwoConcrete{RootInterface: one})

    _, ok := two.(TwoConcrete)
    fmt.Println(ok) // prints true

    // How can I get the equivalent of ok == true,
    // i.e. find out that OneConcrete is the acutal
    // RootInterface implementation?
    _, ok = two.(OneConcrete)
    fmt.Println(ok) // prints false
}

Note that I would like an answer to the general case where RootInterface could be embedded arbitrarily deeply within a struct hierarchy.

Answer 1

OneConcrete does not embeds interface. It implements that interface. Embedding a type mean that struct will get one additional field with same name as given type and all methods of that type will become methods of struct. So, to get OneConcrete you should do two.(TwoConcrete).RootInterface.(OneConcrete).