Golang设计模式,装饰器模式

package decorator
import (
 "errors"
 "fmt"
)
type IngredientAdder interface {
 AddIngredient() (string, error)
}
type PizzaDecorator struct {
 Ingredient IngredientAdder
}
func (p *PizzaDecorator) AddIngredient() (string, error) {
 return "Pizza with the following ingredients:", nil
}
type Meat struct {
 Ingredient IngredientAdder
}
func (m *Meat) AddIngredient() (string, error) {
 if m.Ingredient == nil {
 return "", errors.New("An IngredientAdder is needed on the Ingredient field of the Meat") 
 }
 s, err := m.Ingredient.AddIngredient()
 if err != nil {
 return "", err
 }
 return fmt.Sprintf("%s %s", s, "meat"), nil
}
type Onion struct {
 Ingredient IngredientAdder
}
func (o *Onion) AddIngredient() (string, error) {
 if o.Ingredient == nil {
 return "", errors.New("An IngredientAdder is needed on the Ingredient field of the Onion")
 }
 s, err := o.Ingredient.AddIngredient()
 if err != nil {
 return "", err
 }
 return fmt.Sprintf("%s %s", s, "onion"), nil
}

装饰器模式测试

package decorator
import (
 "strings"
 "testing"
)
func TestPizzaDecorator_AddIngredient(t *testing.T) {
 pizza := &PizzaDecorator{}
 pizzaResult, err := pizza.AddIngredient()
 if err != nil {
 t.Error(err)
 }
 expectedText := "Pizza with the following ingredients:"
 if !strings.Contains(pizzaResult, expectedText) {
 t.Errorf("When calling the add ingredient of the pizza decorator it "+ 
 "must return the text %s, not '%s'", expectedText, pizzaResult)
 }
}
func TestOnion_AddIngredient(t *testing.T) {
 onion := &Onion{}
 onionResult, err := onion.AddIngredient()
 if err == nil {
 t.Errorf("When calling AddIngredient on the onion decorator without "+
 "an IngredientAdder on its Ingredient field it must return an error, "+
 "not a string with '%s'", onionResult)
 } 
 onion = &Onion{&PizzaDecorator{}}
 onionResult, err = onion.AddIngredient()
 if err != nil {
 t.Error(err)
 } 
 if !strings.Contains(onionResult, "onion") {
 t.Errorf("When calling the add ingredient of the onion decorator it "+
 "must return a text with the word 'onion', not '%s'", onionResult)
 }
}
func TestMeat_AddIngredient(t *testing.T) {
 meat := &Meat{}
 meatResult, err := meat.AddIngredient()
 if err == nil {
 t.Errorf("When calling AddIngredient on the meat decorator without " +
 "an IngredientAdder on its Ingredient field must return an error, " +
 "not a string with '%s'", meatResult)
 }
 meat = &Meat{&PizzaDecorator{}}
 meatResult, err = meat.AddIngredient()
 if err != nil {
 t.Error(err)
 } 
 if !strings.Contains(meatResult, "meat") {
 t.Errorf("When calling the AddIngredient of the meat decorator it "+
 "must return a text with the word 'meat', not '%s'", meatResult)
 }
}
func TestPizzaDecorator_FullStack(t *testing.T) {
 pizza := &Onion{&Meat{&PizzaDecorator{}}}
 pizzaResult, err := pizza.AddIngredient()
 if err != nil {
 t.Error(err)
 } 
 expectedText := "Pizza with the following ingredients: meat onion"
 if !strings.Contains(pizzaResult, expectedText) {
 t.Errorf("When asking for a pizza with onion and meat the returned "+
 "string must contain the text '%s' but '%s' didn't have it", expectedText,
 pizzaResult)
 }
}

本文来自:简书

感谢作者:aside section ._1OhGeD

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