可以在一个结构体中嵌套另一个结构体以满足接口的要求。

huangapple
go评论121阅读模式
英文:

Can One Embed A Struct In A Struct To Satisfy An Interface

问题

我有以下代码（也可以在Go Playground中找到）。是否可能实例化一个包含嵌入式C、S和X的A结构体？我使用接口的原因是，根据我调用的Build函数，我希望拥有具有不同Bar()实现的结构体。我可以有一个S1或S2，其中Bar()略有不同，但都是S'ers。

  1. package main
  3. import "fmt"
  5. type Cer interface {
  6. 	Foo()
  7. }
  9. type Ser interface {
  10. 	Bar()
  11. }
  13. type Aer interface {
  14. 	Cer
  15. 	Ser
  16. }
  18. type C struct {
  19. 	CField string
  20. }
  22. func (this *C) Foo() {
  23. }
  25. type S struct {
  26. 	SField string
  27. }
  29. func (this *S) Bar() {
  30. }
  32. type X struct {
  33. 	XField string
  34. }
  36. type A struct {
  37. 	Cer
  38. 	Ser
  39. 	X
  40. }
  42. func main() {
  43. 	x := new(X)
  44. 	a := Build(x)
  45. 	fmt.Println(a)
  46. }
  48. func Build(x *X) A {
  49. 	a := new(A)
  50. 	a.X = *x
  51. 	a.XField = "set x"
  52. 	return *a
  53. }
英文:

I have the following code (also available in the Go Playground). Is it possible to instantiate an A struct such that it contains an embedded C, S and an X. The reason I am using interfaces is because, depending on the Build function I call, I'd like to have structs that have different implementations of Bar(). I could have an S1 or an S2, where Bar() is slightly different, but both are S'ers.

  1. package main
  3. import "fmt"
  5. type Cer interface {
  6. 	Foo()
  7. }
  9. type Ser interface {
  10. 	Bar()
  11. }
  13. type Aer interface {
  14. 	Cer
  15. 	Ser
  16. }
  18. type C struct {
  19. 	CField string
  20. }
  22. func (this *C) Foo() {
  23. }
  25. type S struct {
  26. 	SField string
  27. }
  29. func (this *S) Bar() {
  30. }
  32. type X struct {
  33. 	XField string
  34. }
  36. type A struct {
  37. 	Cer
  38. 	Ser
  39. 	X
  40. }
  42. func main() {
  43. 	x := new(X)
  44. 	a := Build(x)
  45. 	fmt.Println(a)
  46. }
  48. func Build(x *X) A {
  49. 	a := new(A)
  50. 	a.X = *x
  51. 	a.XField = "set x"
  52. 	return *a
  53. }

答案1

得分: 1

简短回答是：是的，你可以。

但是，当嵌入接口时，如果在调用嵌入的方法之前没有先给定一个值，你将会遇到运行时错误。

所以，下面的代码是正确的：

  1. a := Build(x)
  2. // 如果删除下面这行代码，在调用 a.Foo() 时将会导致运行时错误
  3. a.Cer = &C{"The CField"}
  4. a.Foo()
英文:

Short answer is: Yes, you can.

But when embedding interfaces, you will have a runtime error incase you try to call the embedded method without having given a value first.

So, the following works fine:

  1. a := Build(x)
  2. // Removing the line below will cause a runtime error when calling a.Foo()
  3. a.Cer = &C{"The CField"}
  4. a.Foo()

huangapple
  • 本文由 发表于 2014年5月6日 11:35:24
  • 转载请务必保留本文链接：https://go.coder-hub.com/23485542.html
  • embedding
  • go
  • interface
  • struct
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