英文:
cannot use children (type []Child) as type []Node in argument to func
问题
以下是你提供的代码的翻译：
这是我的测试代码
package main
import "fmt"
type Node interface {
sayHello()
}
type Parent struct {
Name string
}
type Child struct {
Parent
Age int
}
type Children []Child
func (p Parent) sayHello() {
fmt.Printf("你好，我的名字是%s\n", p.Name)
}
func (p Child) sayHello() {
fmt.Printf("你好，我的名字是%s，我%d岁\n", p.Name, p.Age)
}
func makeSayHello(n Node) {
n.sayHello()
}
func sayHellos(list []Node) {
for _, p := range list {
makeSayHello(p)
}
}
func main() {
children := []Child{Child{Parent: Parent{Name: "Bart"}, Age: 8}, Child{Parent: Parent{Name: "Lisa"}, Age: 9}}
for _, c := range children {
c.sayHello()
}
makeSayHello(Parent{"Homer"})
sayHellos([]Node{Parent{"Homer"}})
sayHellos([]Node{Parent{"Homer"}, Child{Parent: Parent{"Maggy"}, Age: 3}})
sayHellos(children) // 错误：无法将类型 []Child 作为类型 []Node 传递给 sayHellos
}
链接：https://play.golang.org/p/7IZLoXjlIK
我不明白。假设我有一个不可修改的 []Child，我想将其与接受 []Parent 的函数一起使用。为什么会出现类型错误？
如果我不能或不想通过更改
children := []Child{...}
为
children := []Node{...}
来解决这个问题，我该怎么办才能将 []Child 转换为 []Node？难道它不是已经是 []Node 吗？我尝试了 children.([]Node) 或 []Node(children)，但没有成功...
英文:
Here is my test code
package main
import "fmt"
type Node interface {
sayHello()
}
type Parent struct {
Name string
}
type Child struct {
Parent
Age int
}
type Children []Child
func (p Parent) sayHello() {
fmt.Printf("Hello my name is %s\n", p.Name)
}
func (p Child) sayHello() {
fmt.Printf("Hello my name is %s and I'm %d\n", p.Name, p.Age)
}
func makeSayHello(n Node) {
n.sayHello()
}
func sayHellos(list []Node) {
for _, p := range list {
makeSayHello(p)
}
}
func main() {
children := []Child{Child{Parent: Parent{Name: "Bart"}, Age: 8}, Child{Parent: Parent{Name: "Lisa"}, Age: 9}}
for _, c := range children {
c.sayHello()
}
makeSayHello( Parent{"Homer"} )
sayHellos( []Node{Parent{"Homer"}} )
sayHellos( []Node{Parent{"Homer"},Child{Parent:Parent{"Maggy"},Age:3}} )
sayHellos( children ) // error : cannot use children (type []Child) as type []Node in argument to sayHellos
}
link https://play.golang.org/p/7IZLoXjlIK
I don't get it. Let's say I have a []Child I cannot modify and I want use it with un function accepting []Parent. Why do I have an type error ?
If I can't or don't want this solution by changing
children := []Child{...}
to
children := []Node{...}
What can I do to transform the []Child to []Node ? It is not already ? Do I have to do another []Node to copy my elements in ?
I naïvely try children.([]Node) or []Node(children) without success ...
答案1
得分: 1
一个结构体数组（比如[]Child）与一个接口数组（比如[]Node）在内存布局上有很大的区别。因此，Go语言不会隐式地将[]Child转换为[]Node，你需要自己进行转换：
nodes := make([]Node, len(children), len(children))
for i := range children {
nodes[i] = children[i]
}
sayHellos(nodes)
顺便提一下，在你提供的示例中，直接调用sayHello会更高效：
for _, child := range children {
child.sayHello()
}
可能这也是你在程序中应该做的事情。
英文:
An array of structs (such as []Child) has very different memory layout comparing to an array of interfaces (such as []Node). So Go doesn't do []Child to []Node conversion implicitly, you have to do it yourself:
nodes := make([]Node, len(children), len(children))
for i := range children {
nodes[i] = children[i]
}
sayHellos(nodes)
BTW in the example you provided it would be more efficient to call sayHello directly:
for _, child := range children {
child.sayHello()
}
Probably this is what you should do in your program as well.
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