英文:
Underlying pointer type from interface value
问题
如何从接口中获取底层指针类型？
package main
import (
"fmt"
)
type Car interface {
Drive() string
}
type MyCar struct {
name string
}
func (MyCar) Drive() string {
return "rum rum"
}
func main() {
var car Car
mycar := &MyCar{name: "mycar"}
car = mycar
mycarptr, err := car.(*MyCar)
mycarvalue, err2 := car.(MyCar)
fmt.Printf("as ptr failed: %t, as value failed: %t\n", err, err2)
fmt.Printf("as ptr: %+v, as value: %+v", mycarptr, mycarvalue)
}
你可以使用类型断言来获取接口的底层指针类型。在上面的代码中，car.(*MyCar) 将返回一个指向 MyCar 类型的指针，而 car.(MyCar) 将返回一个 MyCar 类型的值。如果类型断言失败，将返回一个错误。
英文:
How do I get the underlying pointer type from an interface?
package main
import (
"fmt"
)
type Car interface {
Drive() string
}
type MyCar struct {
name string
}
func (MyCar) Drive ( ) string {
return "rum rum"
}
func main() {
var car Car
mycar := &MyCar{name:"mycar"}
car = mycar
mycarptr, err := car.(*MyCar)
mycarvalue, err2 := car.(MyCar)
fmt.Printf( "as ptr failed: %t, as value failed: %t\n", err, err2 )
fmt.Printf( "as ptr: %+v, as value: %+v", mycarptr, mycarvalue)
}
答案1
得分: 0
你对 *MyCar 的第一个断言是正确的。
这是一个示例 playground 来说明。
对于 MyCar 的第二个断言将会失败，因为它不是一个指针。
英文:
Your first assertion to *MyCar works fine
Here is a playground example to illustrate
Your second assertion to MyCar will fail since it's not a pointer.
答案2
得分: 0
要能够修改汽车，你需要使用指向它的指针（就像你已经做的那样），但为了让其他人（包括你自己）更清楚，你应该在指针上定义接口方法：
type Drivable interface {
Drive() string
}
type Car struct {
name string
}
func (*Car) Drive() string {
return "rum rum"
}
type SpaceShip struct {
name string
}
func (*SpaceShip) Drive() string {
return "当你驾驶/飞行它们时，太空船发出的声音"
}
func Drive(d Drivable) {
switch d := d.(type) { // d 现在是实际类型
case *Car:
fmt.Println("得到了一辆名为", d.name, "的汽车")
case *SpaceShip:
fmt.Println("得到了一艘名为", d.name, "的太空船")
}
}
我建议你阅读《Effective Go》，特别注意《接口和方法》部分。
英文:
To be able to modify the car you need to use a pointer to it (like you already did), however to make it more clear to others (and yourself) you should define the interface method on the pointer:
type Drivable interface {
Drive() string
}
type Car struct {
name string
}
func (*Car) Drive() string {
return "rum rum"
}
type SpaceShip struct {
name string
}
func (*SpaceShip) Drive() string {
return "sound spaceships makes when you drive / fly them"
}
func Drive(d Drivable) {
switch d := d.(type) { // d now is the actual type
case *Car:
fmt.Println("Got a car named", d.name)
case *SpaceShip:
fmt.Println("Got a spaceship named", d.name)
}
}
I recommend going through Effective Go, and pay extra attention to the Interfaces And Methods section.
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