Inheritance substitute for method parameters in Go

I understood that Go has no inheritance and works with composition.

Here is my small example:

type Car struct {
    XMLName xml.Name `xml:"response"`
    // some properties coming from a XML file
}

type Audi struct {
    Car
    // some more properties coming from a XML file
}

func UnmarshalFromXML(url string, car *Car) { /* fill the properties from the XML file */ }

What I actually want:

var audi Audi
UnmarshalFromXML("someURL", &audi)

But this does not work, because there is no inheritance. But I need structs to use the unmarshal functionality for XML files.

So what to do?

Inheritance in go very different from another languages. When a type extended from a parent type, the two types remain distinct. The solution in your case is to create an interface, and pass interface as parameter in the function. Take a look to the example below:

package main

import (
	"fmt"
)

// creating an interface
type Vehicle interface {
	Move()
}

type Car struct {
	Color string
	Brand string
}

// Car has method Move(), automatically stated implement Vehicle interface
func (c *Car) Move() {
	fmt.Print("Car is moving")
}

func(c *Car) Honk() {
	fmt.Print("Teeeet... Teet")
}

type Audi struct {
	EngineType string
	Car
}

// passing an interface
func UnmarshalFromXML(url string, v Vehicle) { 
	fmt.Print(v)
	v.Honk() 
	
}


func main() {
	var car = Car{Color:"Green"}
	var audi = Audi{}
	audi.Car = car
	audi.Brand = "Audi"
	audi.EngineType = "EC"
	
	UnmarshalFromXML("someURL", &audi)
}

https://play.golang.org/p/ZO4P_3fjmz

This article have a great explanation of OOP in go: http://spf13.com/post/is-go-object-oriented/

You could try using interfaces instead

    type Car interface {
       theCar()
    }

    type CarBase struct {
    }

    func (_ CarBase) theCar() {
    }
      
    type Audi struct {
      CarBase
    }

    func UnmarshalFromXML(url string, car Car)