如何使多个接口引用相同的值？

huangapple
go评论132阅读模式
英文:

How do you make multiple interfaces reference the same value?

问题

我想让两个接口引用相同的值（也就是说，如果你更新其中一个，另一个也会更新为相同的内容）：

  1. package main
  3. import (
  4.     "fmt"
  5. )
  7. func main() {
  8.     var a, b interface{}
  10.     a = "Hi"
  12.     b = &a
  13.     a = *b.(*interface{})
  15.     b = "Howdy"
  17.     fmt.Println(a)
  18.     fmt.Println(b)
  19. }

打印日志

  1. Howdy
  2. Howdy

PLAYGROUND: 点击这里

这段代码可以按预期工作，除了a和b不是接口类型。所以当我将它们转换为接口类型时...

  1. package main
  3. import (
  4.     "fmt"
  5. )
  7. func main() {
  8.     var a, b interface{}
  10.     a = "Hi"
  12.     b = *(&a)
  13.     a = *(&b)
  15.     b = "Howdy"
  17.     fmt.Println(a)
  18.     fmt.Println(b)
  19. }

打印日志

  1. Hi
  2. Howdy

PLAYGROUND: 点击这里

...这段代码不再按预期工作。

有没有一种方法可以使用接口数据类型而不是reflect.Value数据类型，并且保持两个接口引用相同的值？

英文:

I would like to make two interfaces reference the same value (meaning if you update one, the other will update to the same thing):

  1. package main
  3. import (
  4.     "fmt"
  5.     "reflect"
  6. )
  8. func main(){
  9.     var a, b any
  11.     a = "Hi"
  13.     b = reflect.ValueOf(&a).Elem()
  14.     a = reflect.ValueOf(&b).Elem()
  16.     b = "Howdy"
  18.     fmt.Println(a)
  19.     fmt.Println(b)
  20. }

PRINT LOGS

  1. Howdy
  2. Howdy

PLAYGROUND: https://go.dev/play/p/qizVO42UaUj

This code works as intended, aside from the fact that a and b are not interfaces. So when I convert them to interfaces like so...

  1. package main
  3. import (
  4.     "fmt"
  5.     "reflect"
  6. )
  8. func main(){
  9.     var a, b any
  11.     a = "Hi"
  13.     b = reflect.ValueOf(&a).Elem().Interface()
  14.     a = reflect.ValueOf(&b).Elem().Interface()
  16.     b = "Howdy"
  18.     fmt.Println(a)
  19.     fmt.Println(b)
  20. }

PRINT LOGS

  1. Hi
  2. Howdy

PLAYGROUND: https://go.dev/play/p/jCpuepBJYdD

...the code no longer works as intended.

Is there a way to use the interface data type rather than the reflect.Value data type while maintaining that the two interfaces reference the same value?

答案1

得分: 0

简单解决方案

找到了解决方法，不需要使用反射。通过将值的地址存储在接口中，可以通过使用类型断言到接口指针并解引用来实现：

  1. package main
  3. import "fmt"
  5. func main() {
  6. 	var object any
  7. 	object = "Hi"
  9. 	var a, b any
  10. 	a = &object
  11. 	b = &object
  13. 	*a.(*any) = "Howdy"
  15. 	fmt.Println(*a.(*any))
  16. 	fmt.Println(*b.(*any))
  17. }

打印日志

  1. Howdy
  2. Howdy

PLAYGROUND: https://go.dev/play/p/LEx8MR4ZK06

使用多个函数

如果你想要抽象出类型断言和解引用的过程：

  1. package main
  3. import "fmt"
  5. func getStuff(a any) any {
  6. 	return *a.(*any)
  7. }
  9. func setStuff(a, to any) {
  10. 	*a.(*any) = to
  11. }
  13. func main() {
  14. 	var object any
  15. 	object = "Hi"
  17. 	var a, b any
  18. 	a = &object
  19. 	b = &object
  21. 	setStuff(a, "Howdy")
  23. 	fmt.Println(getStuff(a))
  24. 	fmt.Println(getStuff(b))
  25. }

打印日志

  1. Howdy
  2. Howdy

PLAYGROUND: https://go.dev/play/p/RUX4cu2Cx2o

英文:

<h1>Simple Solution</h1>

Figured it out—no need to use reflection. Storing the value's address in the interface will allow you to accomplish this by using a type assertion to an interface pointer and dereferencing:

  1. package main
  3. import &quot;fmt&quot;
  5. func main() {
  6. 	var object any
  7. 	object = &quot;Hi&quot;
  9. 	var a, b any
  10. 	a = &amp;object
  11. 	b = &amp;object
  13. 	*a.(*any) = &quot;Howdy&quot;
  15. 	fmt.Println(*a.(*any))
  16. 	fmt.Println(*b.(*any))
  17. }

PRINT LOGS

  1. Howdy
  2. Howdy

PLAYGROUND: https://go.dev/play/p/LEx8MR4ZK06

<h1>Using Multiple Functions</h1>

If you would like to abstract away the type-assertion and derefencing:

  1. package main
  3. import &quot;fmt&quot;
  5. func getStuff(a any) any {
  6. 	return *a.(*any)
  7. }
  9. func setStuff(a, to any) {
  10. 	*a.(*any) = to
  11. }
  13. func main() {
  14. 	var object any
  15. 	object = &quot;Hi&quot;
  17. 	var a, b any
  18. 	a = &amp;object
  19. 	b = &amp;object
  21. 	setStuff(a, &quot;Howdy&quot;)
  23. 	fmt.Println(getStuff(a))
  24. 	fmt.Println(getStuff(b))
  25. }

PRINT LOGS

  1. Howdy
  2. Howdy

PLAYGROUND: https://go.dev/play/p/RUX4cu2Cx2o

huangapple
  • 本文由 发表于 2022年9月14日 03:06:06
  • 转载请务必保留本文链接：https://go.coder-hub.com/73708149.html
  • go
  • interface
  • memory
  • memory-management
  • reflection
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