手撸golang 架构设计原则 接口隔离原则
缘起
最近复习设计模式
拜读谭勇德的<<设计模式就该这样学>>
本系列笔记拟采用golang练习之
接口隔离原则
接口隔离原则（Interface Segregation Principle, ISP）指用多个专门的接口，而不使用单一的总接口，客户端不应该依赖它不需要的接口。设计接口时，应当注意以下几点:
（1）一个类对另一个类的依赖应该建立在最小接口上。
（2）建立单一接口，不要建立庞大臃肿的接口。
（3）尽量细化接口，接口中的方法尽量少。
_
场景
- 设计一个动物接口
- 不同动物可能有eat(), fly(), swim()等方法
- 设计实现动物接口的Bird类和Dog类
IBadAnimal.go
不好的接口设计, 接口方法很多, 比较臃肿, 需要实现接口时负担很重
package interface_segregation
type IBadAnimal interface {
ID() int
Name() string
Eat() error
Fly() error
Swim() error
}BadBird.go
BadBird实现了IBadAnimal接口.
BadBird是不支持Swim()的, 但由于接口要求, 只能返回无意义的错误应付.
package interface_segregation
import (
"errors"
"fmt"
)
type BadBird struct {
iID int
sName string
}
func NewBadBird(id int, name string) IBadAnimal {
return &BadBird{
iID: id,
sName: name,
}
}
func (me *BadBird) ID() int {
return me.iID
}
func (me *BadBird) Name() string {
return me.sName
}
func (me *BadBird) Eat() error {
fmt.Printf("%v/%v is eating\n", me.Name(), me.ID())
return nil
}
func (me *BadBird) Fly() error {
fmt.Printf("%v/%v is flying\n", me.Name(), me.ID())
return nil
}
func (me *BadBird) Swim() error {
return errors.New(fmt.Sprintf("%v/%v cannot swimming", me.Name(), me.ID()))
}
BadDog.go
BadDog实现IBadAnimal接口.
本来BadDog是不支持Fly()方法的, 但由于接口要求, 因此只能返回无意义错误.
package interface_segregation
import (
"errors"
"fmt"
)
type BadDog struct {
iID int
sName string
}
func NewBadDog(id int, name string) IBadAnimal {
return &BadDog{
iID: id,
sName: name,
}
}
func (me *BadDog) ID() int {
return me.iID
}
func (me *BadDog) Name() string {
return me.sName
}
func (me *BadDog) Eat() error {
fmt.Printf("%v/%v is eating\n", me.Name(), me.ID())
return nil
}
func (me *BadDog) Fly() error {
return errors.New(fmt.Sprintf("%v/%v cannot fly", me.Name(), me.ID()))
}
func (me *BadDog) Swim() error {
fmt.Printf("%v/%v is swimming\n", me.Name(), me.ID())
return nil
}IGoodAnimal.go
更好的接口设计. 将动物接口拆分为基本信息接口IGoodAnimal, 以及三个可选的能力接口:
ISupportEat, ISupportFly, ISupportSwim
package interface_segregation
type IGoodAnimal interface {
ID() int
Name() string
}
type ISupportEat interface {
Eat() error
}
type ISupportFly interface {
Fly() error
}
type ISupportSwim interface {
Swim() error
}GoodAnimalInfo.go
实现IGoodAnimal接口, 提供动物的id,name等基本属性
package interface_segregation
type GoodAnimalInfo struct {
iID int
sName string
}
func (me *GoodAnimalInfo) ID() int {
return me.iID
}
func (me *GoodAnimalInfo) Name() string {
return me.sName
}GoodBird.go
更好的Bird实现, 异味代码更少.
通过集成GoodAnimalInfo实现IGoodAnimal接口, 并选择性实现ISupportEat, ISupportFly.
package interface_segregation
import "fmt"
type GoodBird struct {
GoodAnimalInfo
}
func NewGoodBird(id int, name string) IGoodAnimal {
return &GoodBird{
GoodAnimalInfo{
id,
name,
},
}
}
func (me *GoodBird) Eat() error {
fmt.Printf("%v/%v is eating\n", me.Name(), me.ID())
return nil
}
func (me *GoodBird) Fly() error {
fmt.Printf("%v/%v is flying\n", me.Name(), me.ID())
return nil
}GoodDog.go
更好的Dog实现, 异味代码更少.
通过集成GoodAnimalInfo实现IGoodAnimal接口, 并选择性实现ISupportEat, ISupportSwim.
package interface_segregation
import "fmt"
type GoodDog struct {
GoodAnimalInfo
}
func NewGoodDog(id int, name string) IGoodAnimal {
return &GoodDog{
GoodAnimalInfo{
id,
name,
},
}
}
func (me *GoodDog) Eat() error {
fmt.Printf("%v/%v is eating\n", me.Name(), me.ID())
return nil
}
func (me *GoodDog) Swim() error {
fmt.Printf("%v/%v is swimming\n", me.Name(), me.ID())
return nil
}interface_segregation_test.go
单元测试
package main
import (
isp "learning/gooop/principles/interface_segregation"
"testing"
)
func Test_ISP(t *testing.T) {
fnLogIfError := func(fn func() error) {
e := fn()
if e != nil {
t.Logf("error = %s\n", e.Error())
}
}
fnTestBadAnimal := func (a isp.IBadAnimal) {
fnLogIfError(a.Eat)
fnLogIfError(a.Fly)
fnLogIfError(a.Swim)
}
fnTestBadAnimal(isp.NewBadBird(1, "BadBird"))
fnTestBadAnimal(isp.NewBadDog(2, "BadDog"))
fnTestGoodAnimal := func(a isp.IGoodAnimal) {
if it,ok := a.(isp.ISupportEat);ok {
fnLogIfError(it.Eat)
} else {
t.Logf("%v/%v cannot eat", a.Name(), a.ID())
}
if it,ok := a.(isp.ISupportFly);ok {
fnLogIfError(it.Fly)
} else {
t.Logf("%v/%v cannot fly", a.Name(), a.ID())
}
if it,ok := a.(isp.ISupportSwim);ok {
fnLogIfError(it.Swim)
} else {
t.Logf("%v/%v cannot swim", a.Name(), a.ID())
}
}
fnTestGoodAnimal(isp.NewGoodBird(11, "GoodBird"))
fnTestGoodAnimal(isp.NewGoodDog(12, "GoodDog"))
}测试输出
$ go test -v interface_segregation_test.go
=== RUN Test_ISP
BadBird/1 is eating
BadBird/1 is flying
interface_segregation_test.go:12: error = BadBird/1 cannot swimming
BadDog/2 is eating
interface_segregation_test.go:12: error = BadDog/2 cannot fly
BadDog/2 is swimming
GoodBird/11 is eating
GoodBird/11 is flying
interface_segregation_test.go:42: GoodBird/11 cannot swim
GoodDog/12 is eating
interface_segregation_test.go:36: GoodDog/12 cannot fly
GoodDog/12 is swimming
--- PASS: Test_ISP (0.00s)
PASS
ok command-line-arguments 0.002s