go语言设计模式之decorator

decorator.go

package decorator

import (
	"errors"
	"fmt"
)

type IngredientAdd interface {
	AddIngredient() (string, error)
}

type PizzaDecorator struct {
	Ingredient IngredientAdd
}

func (p *PizzaDecorator) AddIngredient() (string, error) {
	return "Pizza with the following ingredients:", nil
}

type Meat struct {
	Ingredient IngredientAdd
}

func (p *Meat) AddIngredient() (string, error) {
	return "", errors.New("Not implemented yet")
}

type Onion struct {
	Ingredient IngredientAdd
}

func (o *Onion) AddIngredient() (string, error) {
	if o.Ingredient == nil {
		return "", errors.New("An IngredientAdd is needed.")
	}
	s, err := o.Ingredient.AddIngredient()
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("%s %s", s, "onion"), nil
}

　　

decorator_test.go

package decorator

import (
	"strings"
	"testing"
)

func TestPizza_AddIngredient(t *testing.T) {
	pizza := &PizzaDecorator{}
	pizzaResult, _ := pizza.AddIngredient()
	expectedText := "Pizza with the following ingredients:"

	if !strings.Contains(pizzaResult, expectedText) {
		t.Error("strings.Contains(pizzaResult, expectedText)")
	}
}

func TestOnion_AddIngredient(t *testing.T) {
	onion := &Onion{}
	onionResult, err := onion.AddIngredient()

	if err == nil {
		t.Error(err)
	}

	onion = &Onion{&PizzaDecorator{}}
	onionResult, err = onion.AddIngredient()
	if err != nil {
		t.Error(err)
	}

	if !strings.Contains(onionResult, "onion") {
		t.Error(`!strings.Contains(onionResult, "onion")`)
	}
}