composable.go

package main

import "fmt"

type XConfig struct {
	Value int
}

type YConfig struct {
	Value int
}

type LogConfig struct {
}

type Log struct {
}

type X struct {
	Log
	value int
}

type Y struct {
	X
	value int
}

func (this *Log) Init(config LogConfig) (*Log, error) {
	return this, nil
}

func (this *Log) Print(format string) {
	fmt.Println("Log:", format)
}

func (this *X) Init(config XConfig) (*X, error) {
	if _, err := this.Log.Init(LogConfig{}); err != nil {
		return nil, err
	}
	this.Print("X Init")
	this.value = config.Value
	return this, nil
}

func (this *Y) Init(config YConfig) (*Y, error) {
	if _, err := this.X.Init(XConfig{config.Value + 1}); err != nil {
		return nil, err
	}
	this.Print("Y Init")
	this.value = config.Value
	return this, nil
}

func (this *Log) String() string {
	return fmt.Sprintf("Log{ }")
}

func (this *X) String() string {
	return fmt.Sprintf("X{ %v %v }", this.value, this.Log.String())
}

func (this *Y) String() string {
	return fmt.Sprintf("Y{ %v %v }", this.value, this.X.String())
}

func main() {
	if this, err := new(Y).Init(YConfig{100}); err != nil {
		fmt.Println(err)
	} else {
		this.Print(fmt.Sprint(this))
	}
}