如何将字段作为参数传递

huangapple
go评论119阅读模式
英文:

How to pass field as parameter

问题

我想将字段作为参数传递给函数来返回值。

  1. package main
  3. import (
  4. 	"fmt"
  5. )
  7. type s struct {
  8. 	a int
  9. 	b int
  10. }
  12. func c(s s, field string) int {
  13. 	var t int
  14. 	if field == "a" {
  15. 		t = s.a
  16. 	} else if field == "b" {
  17. 		t = s.b
  18. 	}
  19. 	return t
  20. }
  22. func main() {
  23. 	fmt.Println(c(s{5, 8}, "b"))
  24. }

有时我想让t = s.a，有时我想让t = s.b来返回值8，问题是如何将它作为参数传递。

英文:

i want to pass field as parameter to return value from function

  1. package main
  3. import (
  4. 	"fmt"
  5. )
  7. type s struct {
  8. 	a int
  9. 	b int
  10. }
  12. func c(s s) int {
  13. 	var t int
  14. 	t = s.a // how to change this to t=s.b just by pass parameter
  15. 	return t
  16. }
  17. func main() {
  18. 	fmt.Println(c(s{5, 8}))
  19. }

some times i want to make t = s.a and other time i wanted t = s.b to return value 8 the question is how to pass it like parameter

https://play.golang.org/p/JisnrTxF2EY

答案1

得分: 2

你可以添加第二个参数来指示你想要的字段，例如：

  1. func c2(s s, field int) int {
  2.     var t int
  3.     switch field {
  4.     case 0:
  5.         t = s.a
  6.     case 1:
  7.         t = s.b
  8.     }
  9.     return t
  10. }

或者更方便的方法是传递字段的名称，并使用反射来获取该字段：

  1. func c3(s s, fieldName string) int {
  2.     var t int
  3.     t = int(reflect.ValueOf(s).FieldByName(fieldName).Int())
  4.     return t
  5. }

或者你可以传递字段的地址，并赋值指向的值：

  1. func c4(f *int) int {
  2.     var t int
  3.     t = *f
  4.     return t
  5. }

测试上述解决方案：

  1. x := s{5, 8}
  3. fmt.Println("c2 with a:", c2(x, 0))
  4. fmt.Println("c2 with b:", c2(x, 1))
  6. fmt.Println("c3 with a:", c3(x, "a"))
  7. fmt.Println("c3 with b:", c3(x, "b"))
  9. fmt.Println("c4 with a:", c4(&x.a))
  10. fmt.Println("c4 with b:", c4(&x.b))

输出结果为：

  1. c2 with a: 5
  2. c2 with b: 8
  3. c3 with a: 5
  4. c3 with b: 8
  5. c4 with a: 5
  6. c4 with b: 8

你可以在Go Playground上尝试运行以上代码。

英文:

You may add a 2nd parameter to signal which field you want, for example:

  1. func c2(s s, field int) int {
  2. 	var t int
  3. 	switch field {
  4. 	case 0:
  5. 		t = s.a
  6. 	case 1:
  7. 		t = s.b
  8. 	}
  9. 	return t
  10. }

Or a more convenient way is to pass the name of the field, and use reflection to get that field:

  1. func c3(s s, fieldName string) int {
  2. 	var t int
  3. 	t = int(reflect.ValueOf(s).FieldByName(fieldName).Int())
  4. 	return t
  5. }

Or you may pass the address of the field, and assign the pointed value:

  1. func c4(f *int) int {
  2. 	var t int
  3. 	t = *f
  4. 	return t
  5. }

Testing the above solutions:

  1. x := s{5, 8}
  3. fmt.Println("c2 with a:", c2(x, 0))
  4. fmt.Println("c2 with b:", c2(x, 1))
  6. fmt.Println("c3 with a:", c3(x, "a"))
  7. fmt.Println("c3 with b:", c3(x, "b"))
  9. fmt.Println("c4 with a:", c4(&x.a))
  10. fmt.Println("c4 with b:", c4(&x.b))

Which will output (try it on the Go Playground):

  1. c2 with a: 5
  2. c2 with b: 8
  3. c3 with a: 5
  4. c3 with b: 8
  5. c4 with a: 5
  6. c4 with b: 8

huangapple
  • 本文由 发表于 2021年11月11日 00:32:24
  • 转载请务必保留本文链接：https://go.coder-hub.com/69916911.html
  • go
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