Can Embedded Go Methods Access Parent Struct Fields?

Can Embedded Methods Access Parent Fields?

In Go, embedded methods are a powerful mechanism for code reuse and organization. However, a common question arises: can embedded methods directly access the fields of their parent struct?

Background

For context, suppose you're creating an Active Record-style ORM for Go where common CRUD methods are embedded in the user struct for readability and abstraction. This would allow you to write user.Save() instead of data.Save(user).

Example

Consider this code snippet:

package main

import (
    "fmt"
    "reflect"
)

func main() {
    test := Foo{Bar: &Bar{}, Name: "name"}
    test.Test()
}

type Foo struct {
    *Bar
    Name string
}

func (s *Foo) Method() {
    fmt.Println("Foo.Method()")
}

type Bar struct {
}

func (s *Bar) Test() {
    t := reflect.TypeOf(s)
    v := reflect.ValueOf(s)
    fmt.Printf("model: %+v %+v %+v\n", s, t, v)
    fmt.Println(s.Name)
    s.Method()
}

Question Revisited

The question at hand is whether there's a way to make top-level fields accessible from embedded methods. In the example above, the Test method is embedded in Bar and attempts to access the Name field from the parent Foo struct.

Answer

Unfortunately, Go does not provide any direct mechanism for embedded methods to access the fields of their parent struct. The receiver of the Test method is a pointer to Bar, and there is no way for Go to determine if it is embedded or not.

Possible Solution

To achieve this functionality, one potential workaround is to add an interface{} member to the Bar struct, requiring that types that implement it set the member to the containing type. The initialization of this member could either be the responsibility of the caller or handled through an ORM method. However, this approach introduces additional complexity and potential maintenance issues.

Alternative Perspective

Alternatively, consider the possibility that structuring the API as db.Save(user) may not be as detrimental as it seems. This approach offers a straightforward way to support multiple databases and avoids relying on global state.

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