如何在Golang中返回一个未知类型的数组？

huangapple
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英文:

How to return an array of unknown type in Golang?

问题

所以我有一个方法，需要返回一个数组，但我不知道要返回什么类型的数组。
返回的数组类型取决于方法的逻辑。

我的方法看起来像这样...

  1. func (c Case) GetFrdValues(frdFieldKey string) (interface{}, error) {
  2.     for _, singleFrd := range c.CaseDetails.GetCase().GetFrds() {
  3.         if singleFrd.GetIdentifier().GetFieldKey() == frdFieldKey {
  4.             switch singleFrd.GetValue().WhichType() {
  5.             case casespb.Value_StringValue_case:
  6.                 return []string{singleFrd.GetValue().GetStringValue()}, nil
  7.             case casespb.Value_NumberValue_case:
  8.                 return [1]float64{singleFrd.GetValue().GetNumberValue()}, nil
  9.             case casespb.Value_BoolValue_case:
  10.                 return [1]bool{singleFrd.GetValue().GetBoolValue()}, nil
  11.             case casespb.Value_NullValue_case:
  12.                 return []string{}, nil
  13.             case casespb.Value_ListValue_case:
  14.                 return GetValuesFromFrdListValue(singleFrd.GetValue().GetListValue())
  15.             default:
  16.                 return []string{}, nil
  17.             }
  18.         }
  19.     }
  20.     return []string{}, fmt.Errorf("Frd Value contains unsupported value type %v", frdFieldKey)
  21. }

这个方法很好用，因为它确实返回了我想要的值的数组。

然而，我需要在另一个方法中操作返回的数组。但是无法对列表（类型为interface{}的变量）进行迭代。

因此，返回的值应该是[]interface{}类型。但是如果我这样做，那么我在各个返回语句上会收到以下错误。

cannot use ([]string literal) (value of type []string) as []interface{} value in return statement.

我在Stack Overflow或者网上找不到任何关于这个问题的解答，所以非常感谢任何帮助！

英文:

So I have a method which needs to return an array but I don't know what type of array to return.
This type of array to return is down to the methods logic.

My method looks like this...

  1. func (c Case) GetFrdValues(frdFieldKey string) (interface{}, error) {
  2. 	for _, singleFrd := range c.CaseDetails.GetCase().GetFrds() {
  3. 		if singleFrd.GetIdentifier().GetFieldKey() == frdFieldKey {
  4. 			switch singleFrd.GetValue().WhichType() {
  5. 			case casespb.Value_StringValue_case:
  6. 				return []string{singleFrd.GetValue().GetStringValue()}, nil
  7. 			case casespb.Value_NumberValue_case:
  8. 				return [1]float64{singleFrd.GetValue().GetNumberValue()}, nil
  9. 			case casespb.Value_BoolValue_case:
  10. 				return [1]bool{singleFrd.GetValue().GetBoolValue()}, nil
  11. 			case casespb.Value_NullValue_case:
  12. 				return []string{}, nil
  13. 			case casespb.Value_ListValue_case:
  14. 				return GetValuesFromFrdListValue(singleFrd.GetValue().GetListValue())
  15. 			default:
  16. 				return []string{}, nil
  17. 			}
  18. 		}
  19. 	}
  20. 	return []string{}, fmt.Errorf("Frd Value contains unsupported value type %v", frdFieldKey)
  21. }

This works fine as it does still return an array of the values I want.

However I need to manipulate the returned array in a separate method. But cannot range over list (variable of type interface{}).

Therefore the returned value needs be like [] interface{}. However if I have it like that then I receive the error on my various return statements about.

cannot use ([]string literal) (value of type []string) as []interface{} value in return statement.

I can't find anything on stack overflow or the web about this, so any help would be greatly appreciated!

答案1

得分: 2

你可以使用反射来遍历一个未知类型的数组。这里有一个简化的示例，它只是打印出数组的元素。

  1. package main
  3. import (
  4. 	"fmt"
  5. 	"reflect"
  6. )
  8. func main() {
  9. 	doSomething([]string{"a", "b", "c"})
  10. 	doSomething([]int{1, 2, 3})
  11. }
  13. func doSomething(item interface{}) {
  14. 	reflectType := reflect.TypeOf(item)
  15. 	if reflectType.Kind() == reflect.Ptr {
  16. 		reflectType = reflectType.Elem()
  17. 	}
  19. 	if reflectType.Kind() != reflect.Slice {
  20. 		fmt.Println("received item is not a slice")
  21. 		return
  22. 	}
  24. 	val := reflect.ValueOf(item)
  26. 	itemLength := val.Len()
  27. 	for i := 0; i < itemLength; i++ {
  28. 		fmt.Println(val.Index(i))
  29. 	}
  30. }

链接：https://play.golang.org/p/5umonjVp90D

英文:

You can use reflection to loop over an array of unknown type. Here is a simplified example that simply prints out the elements of an array.

https://play.golang.org/p/5umonjVp90D

  1. package main
  3. import (
  4. 	&quot;fmt&quot;
  5. 	&quot;reflect&quot;
  6. )
  8. func main() {
  9. 	doSomething([]string{&quot;a&quot;, &quot;b&quot;, &quot;c&quot;})
  10. 	doSomething([]int{1, 2, 3})
  11. }
  13. func doSomething(item interface{}) {
  14. 	reflectType := reflect.TypeOf(item)
  15. 	if reflectType.Kind() == reflect.Ptr {
  16. 		reflectType = reflectType.Elem()
  17. 	}
  19. 	if reflectType.Kind() != reflect.Slice {
  20. 		fmt.Println(&quot;received item is not a slice&quot;)
  21. 		return
  22. 	}
  24. 	val := reflect.ValueOf(item)
  26. 	itemLength := val.Len()
  27. 	for i := 0; i &lt; itemLength; i++ {
  28. 		fmt.Println(val.Index(i))
  29. 	}
  30. }

huangapple
  • 本文由 发表于 2021年6月17日 20:04:30
  • 转载请务必保留本文链接：https://go.coder-hub.com/68018980.html
  • arrays
  • go
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