英文:
issue with interfaces and types
问题
有人能解释一下为什么在将切片传递给可变参数函数时，鸭子类型不起作用吗？
下面的情况1和情况2似乎是可以工作的，但是情况3中，切片被初始化，然后将解引用的切片传递给接受接口的函数。
错误信息是：cannot use gophers (type []Gopher) as type []Animal in argument to runForest
package main
import (
"fmt"
)
type Animal interface {
Run() string
}
type Gopher struct {
}
func (g Gopher) Run() string {
return "Waddle.. Waddle"
}
func runForest(animals ...Animal) {
for _, animal := range animals {
fmt.Println(animal.Run())
}
}
func main() {
//可以工作
runForest(Gopher{})
//可以工作
runForest(Gopher{}, Gopher{})
//不可以工作
gophers := []Gopher{{}, {}}
runForest(gophers...)
}
英文:
Can someone please explain as to why duck typing does not work when a slice is passed to the variadic function.
Cases 1 and 2 as indicated below seems to work, but case-3 below initializes a slice and thereafter passes the dereferenced slice to the function that accepts the interface.
The error message is : cannot use gophers (type []Gopher) as type []Animal in argument to runForest
package main
import (
"fmt"
)
type Animal interface {
Run() string
}
type Gopher struct {
}
func (g Gopher) Run() string {
return "Waddle.. Waddle"
}
func runForest(animals ...Animal) {
for _, animal := range animals {
fmt.Println(animal.Run())
}
}
func main() {
//works
runForest(Gopher{})
//works
runForest(Gopher{},Gopher{})
// does not work
gophers := []Gopher{{},{}}
runForest(gophers...)
}
答案1
得分: 2
如Volker在评论中提到的，切片不能像它们的元素那样隐式转换。一个Gopher可以像一个Animal一样嘎嘎叫，但一个[]Gopher不能像一个[]Animal一样嘎嘎叫。
使其正常工作的最小更改如下：
func main() {
gophers := []Gopher{{}, {}}
out := make([]Animal, len(gophers))
for i, val := range gophers {
out[i] = Animal(val)
}
runForest(out...)
}
英文:
As Volker mentions in the comments, slices can't be implicitly converted the way their elements can. A Gopher can quack like an Animal, but a []Gopher can't quack like an []Animal.
The minimal change to get this working is:
func main() {
gophers := []Gopher{{}, {}}
out := make([]Animal, len(gophers))
for i, val := range gophers {
out[i] = Animal(val)
}
runForest(out...)
}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论