Assert interface with nested struct pointer

Question

I need to assign the struct to an interface{} (a) and then assert it again (b) like in my example. I need MyStruct and MyNestedStruct to be convertible.

https://play.golang.org/p/LSae9dasJI

How can I do that?

Answer 1

In debugging your code I arrived at this (still broken state) which clearly shows what is problematic with your implementation; https://play.golang.org/p/MnyDxKvJsK

The second link has the issue resolved. Basically, your type didn't actually implement the interface because of your return type. Yes the return type implements the interface, but it's not an instance of the interface. Look closely at the code below;

// your version *MyNestedStruct != MyNestedInterface
func (this *MyStruct) GetNested() *MyNestedStruct {
    return this.nested
}

type MyInterface interface{
    GetNested() MyNestedInterface
}

//my version
func (this *MyStruct) GetNested() MyNestedInterface {
    return this.nested
}

https://play.golang.org/p/uf2FfvbATb