go语言设计模式之adapter

package adapter

import (
	"fmt"
)

type LegacyPrinter interface {
	Print(s string) string
}

type MyLegacyPrinter struct{}

func (l *MyLegacyPrinter) Print(s string) (newMsg string) {
	newMsg = fmt.Sprintf("Legacy Printer: %s\n", s)
	fmt.Println(newMsg)
	return
}

type ModernPrinter interface {
	PrintStored() string
}

type PrinterAdapter struct {
	OldPrinter LegacyPrinter
	Msg        string
}

func (p *PrinterAdapter) PrintStored() (newMsg string) {
	if p.OldPrinter != nil {
		newMsg = fmt.Sprintf("Adapter: %s", p.Msg)
		newMsg = p.OldPrinter.Print(newMsg)
	} else {
		newMsg = p.Msg
	}
	return
}

package adapter

import (
	"testing"
)

func TestAdapter(t *testing.T) {
	msg := "Hello World!"
	adapter := PrinterAdapter{OldPrinter: &MyLegacyPrinter{}, Msg: msg}

	returnnedMsg := adapter.PrintStored()

	if returnnedMsg != "Legacy Printer: Adapter: Hello World!\n" {
		t.Errorf("Message didn't match: %s\n", returnnedMsg)
	}

	adapter = PrinterAdapter{OldPrinter: nil, Msg: msg}
	returnnedMsg = adapter.PrintStored()
	if returnnedMsg != "Hello World!" {
		t.Errorf("Message didn't match: %s\n", returnnedMsg)
	}
}