接口
接口的定义
-
接口定义了一个对象化的行为规范
- 只定义规范，不实现
- 具体的对象需要实现规范的细节
- 实践
- type 定义接口 interface
- 接口里面是一组方法签名的集合
type Animal interface {
Talk()
Eat()
Run()
}- 实现
- 一个对象只要包含接口中的方法，那么就实现了这个接口
- 接口类型的变量可以保存实现该接口的任何类型的实例
type Animal interface {
Talk()
Eat()
Run()
}
type Dog struct {
name string
}
//一个对象只要包含接口中的方法，那么就实现了这个接口
func (d *Dog) Eat() {
fmt.Printf("%s is eating\n",d.name)
}
func (d *Dog) Talk() {
fmt.Printf("%s is talking\n",d.name)
}
func (d *Dog) Run() {
fmt.Printf("%s is running\n",d.name)
}
func main() {
var dog = &Dog{
name: "旺财",
}
var a Animal
//接口类型的变量可以保存实现该接口的任何类型的实例
a = dog
a.Eat()
a.Run()
a.Talk()
fmt.Printf("a:%v,dog:%v\n",a,dog)
}接口实例
- 计算公司所有职员的薪水
- 每个职员的计算方式不同
结构体实现
type Developer struct {
Name string
Base float64
}
func (d *Developer)Calc() float64{
return d.Base
}
type PM struct {
Name string
Base float64
Option float64
}
func (p *PM)Calc() float64{
return p.Base + p.Option
}
type YY struct {
Name string
Base float64
Ratio float64
Option float64
}
func (y *YY)Calc() float64 {
return y.Base + y.Option * y.Ratio
}
type EmployeeMgr struct {
devlist []*Developer
pmlist []*PM
yylist []*YY
}
func (e *EmployeeMgr)Calc() float64 {
var sum float64
for _,v := range e.devlist {
sum += v.Calc()
}
for _,v1 := range e.pmlist {
sum += v1.Calc()
}
for _,v2 := range e.yylist {
sum += v2.Calc()
}
return sum
}
func (e *EmployeeMgr)AddDev(d *Developer) {
e.devlist = append(e.devlist, d)
}
func (e *EmployeeMgr)AddPM(p *PM) {
e.pmlist = append(e.pmlist, p)
}
func (e *EmployeeMgr)AddYY(y *YY) {
e.yylist = append(e.yylist, y)
}
func main() {
var e = &EmployeeMgr{}
dev := &Developer{
Name: "develop",
Base: 5000,
}
e.AddDev(dev)
pm := &PM{
Name: "pm",
Base: 10000,
Option: 2000,
}
e.AddPM(pm)
yy := &YY{
Name: "yy",
Base: 23000,
Option: 9000,
Ratio: 0.67,
}
e.AddYY(yy)
sum := e.Calc()
fmt.Printf("sum:%.2f\n",sum)
}接口实现
type Employee interface {
Calc() float64 //接口返回
}
type Developer struct {
Name string
Base float64
}
func (d *Developer)Calc() float64{
return d.Base
}
type PM struct {
Name string
Base float64
Option float64
}
func (p *PM)Calc() float64{
return p.Base + p.Option
}
type YY struct {
Name string
Base float64
Ratio float64
Option float64
}
func (y *YY)Calc() float64 {
return y.Base + y.Option * y.Ratio
}
type EmployeeMgr struct {
employeelist []Employee
}
func (e *EmployeeMgr) Calc() float64 {
var sum float64
for _,v := range e.employeelist {
sum += v.Calc()
}
return sum
}
func (e *EmployeeMgr) AddEmployee(d Employee) {
e.employeelist = append(e.employeelist,d)
}
func main() {
var e = &EmployeeMgr{}
dev := &Developer{
Name: "develop",
Base: 5000,
}
e.AddEmployee(dev)
pm := &PM{
Name: "pm",
Base: 10000,
Option: 2000,
}
e.AddEmployee(pm)
yy := &YY{
Name: "yy",
Base: 23000,
Option: 9000,
Ratio: 0.67,
}
e.AddEmployee(yy)
sum := e.Calc()
fmt.Printf("sum:%.2f\n",sum)
}空接口
- 空接口没有定义任何方法
- 所以了任何类型都实现了空接口
func main() {
var a interface{}
var b int
a = b
fmt.Printf("a=%v,a:%T\n",a,a)
var c float64
a = c
fmt.Printf("a=%v,a:%T\n",a,a)
}类型断言
- 需要引入v,ok := i(T)机制
func Describe(a Animal) {
/*代码有坑
dog := a.(*Dog)
dog.Eat()
*/
dog,ok := a.(*Dog)
if !ok {
fmt.Printf("convert to dog error\n")
return
}
fmt.Printf("describe dog succ\n")
dog.Run()
fmt.Printf("describe dog succ------\n")
}- 类型断言
func DescribeSwitch(a Animal) {
fmt.Printf("DescribeSwitch(a) Begin\n")
switch a.(type) {
case *Dog:
dog := a.(*Dog)
dog.Run()
case *Pig:
pig := a.(*Pig)
pig.Eat()
}
fmt.Printf("DescribeSwitch(a) End\n")
}- 类型断言改进版
func DescribeSwitch(a Animal) {
fmt.Printf("DescribeSwitch(a) Begin\n")
switch v:=a.(type) {
case *Dog:
dog := v
dog.Run()
case *Pig:
pig := v
pig.Eat()
}
fmt.Printf("DescribeSwitch(a) End\n")
}- 指针接收
- 同一个类型可以实现多个接口
type Animal interface {
Talk()
Eat()
Run()
}
type BuRuAnimal interface {
ChiNai()
}
type Dog struct {
name string
}
//一个对象只要包含接口中的方法，那么就实现了这个接口
func (d Dog) Eat() {
fmt.Printf("%s is eating\n",d.name)
}
func (d Dog) Talk() {
fmt.Printf("%s is talking\n",d.name)
}
func (d Dog) Run() {
fmt.Printf("%s is running\n",d.name)
}
func (d Dog) ChiNai() {
fmt.Printf("%s is chinai\n",d.name)
}
func main() {
var dog = &Dog{
name: "旺财",
}
var a Animal
//接口类型的变量可以保存实现该接口的任何类型的实例
a = dog
//Describe(a)
//DescribeSwitch(a)
a.Eat()
var dogVar = Dog{name:"来福"}
a = dogVar
a.Run()
//实现多个接口
var b BuRuAnimal
b = dog
b.ChiNai()
}- 接口嵌套
type Animal interface {
Talk()
Eat()
Run()
}
type BuRuAnimal interface {
ChiNai()
}
type AdvanceAnimal interface {
Animal
BuRuAnimal
}
type Dog struct {
name string
}
//一个对象只要包含接口中的方法，那么就实现了这个接口
func (d Dog) Eat() {
fmt.Printf("%s is eating\n",d.name)
}
func (d Dog) Talk() {
fmt.Printf("%s is talking\n",d.name)
}
func (d Dog) Run() {
fmt.Printf("%s is running\n",d.name)
}
func (d Dog) ChiNai() {
fmt.Printf("%s is chinai\n",d.name)
}
func main() {
var dog = &Dog{
name: "旺财",
}
var a AdvanceAnimal
a = dog
a.ChiNai()
}接口实例详解
- io包中的writer接口
type Test struct {
data string
}
func (t *Test)Write(p []byte) (n int,err error) {
t.data = string(p)
return len(p),nil
}
func FprintfDemo() {
file,_ := os.Create("./a.txt")
fmt.Fprintf(os.Stdout,"hello world\n")
fmt.Fprintf(file,"hello World\n") //终端文件写入
var t *Test = &Test{}
//将字符串写入内存，然后再读取
fmt.Fprintf(t,"this is a test interface %s","dasdada")
fmt.Printf("t.data=%s\n",t.data)
}- fmt包中的Stringer接口
返回字符串
type Student struct {
Name string
Age int
}
func (s *Student)String()string {
data,_ := json.Marshal(s)
return string(data)
}
func main() {
var s = &Student{
Name: "ABC",
Age: 22,
}
fmt.Printf("s = %v\n",s)
}- error接口
type MyError struct {
When time.Time
What string
}
func (e *MyError) Error()string{
str:= fmt.Sprintf("time=%v,message=%s\n",e.When,e.What)
fmt.Printf("1:%T\n",str)
return str
}
func run()error {
fmt.Printf("0\n")
str:=MyError{time.Now(),"it did not work well"}
fmt.Printf("2:%T\n",str)
fmt.Printf("%v,%s\n",time.Now(),"error to run!!")
return &str
}
func main() {
if err := run();err!=nil {
fmt.Printf("3:%T\n",err)
fmt.Println(err)
}
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