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...
func (c Case) GetFrdValues(frdFieldKey string) (interface{}, error) {
for _, singleFrd := range c.CaseDetails.GetCase().GetFrds() {
if singleFrd.GetIdentifier().GetFieldKey() == frdFieldKey {
switch singleFrd.GetValue().WhichType() {
case casespb.Value_StringValue_case:
return []string{singleFrd.GetValue().GetStringValue()}, nil
case casespb.Value_NumberValue_case:
return [1]float64{singleFrd.GetValue().GetNumberValue()}, nil
case casespb.Value_BoolValue_case:
return [1]bool{singleFrd.GetValue().GetBoolValue()}, nil
case casespb.Value_NullValue_case:
return []string{}, nil
case casespb.Value_ListValue_case:
return GetValuesFromFrdListValue(singleFrd.GetValue().GetListValue())
default:
return []string{}, nil
}
}
}
return []string{}, fmt.Errorf("Frd Value contains unsupported value type %v", frdFieldKey)
}
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...
func (c Case) GetFrdValues(frdFieldKey string) (interface{}, error) {
for _, singleFrd := range c.CaseDetails.GetCase().GetFrds() {
if singleFrd.GetIdentifier().GetFieldKey() == frdFieldKey {
switch singleFrd.GetValue().WhichType() {
case casespb.Value_StringValue_case:
return []string{singleFrd.GetValue().GetStringValue()}, nil
case casespb.Value_NumberValue_case:
return [1]float64{singleFrd.GetValue().GetNumberValue()}, nil
case casespb.Value_BoolValue_case:
return [1]bool{singleFrd.GetValue().GetBoolValue()}, nil
case casespb.Value_NullValue_case:
return []string{}, nil
case casespb.Value_ListValue_case:
return GetValuesFromFrdListValue(singleFrd.GetValue().GetListValue())
default:
return []string{}, nil
}
}
}
return []string{}, fmt.Errorf("Frd Value contains unsupported value type %v", frdFieldKey)
}
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。
package main
import (
"fmt"
"reflect"
)
func main() {
doSomething([]string{"a", "b", "c"})
doSomething([]int{1, 2, 3})
}
func doSomething(item interface{}) {
reflectType := reflect.TypeOf(item)
if reflectType.Kind() == reflect.Ptr {
reflectType = reflectType.Elem()
}
if reflectType.Kind() != reflect.Slice {
fmt.Println("received item is not a slice")
return
}
val := reflect.ValueOf(item)
itemLength := val.Len()
for i := 0; i < itemLength; i++ {
fmt.Println(val.Index(i))
}
}
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
package main
import (
"fmt"
"reflect"
)
func main() {
doSomething([]string{"a", "b", "c"})
doSomething([]int{1, 2, 3})
}
func doSomething(item interface{}) {
reflectType := reflect.TypeOf(item)
if reflectType.Kind() == reflect.Ptr {
reflectType = reflectType.Elem()
}
if reflectType.Kind() != reflect.Slice {
fmt.Println("received item is not a slice")
return
}
val := reflect.ValueOf(item)
itemLength := val.Len()
for i := 0; i < itemLength; i++ {
fmt.Println(val.Index(i))
}
}
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