英文:
How to reflect struct recursive in golang
问题
我想递归地反射结构类型和值，但是失败了。我不知道如何递归地传递子结构。
它报错如下：
panic: reflect: NumField of non-struct type
goroutine 1 [running]:
reflect.(*rtype).NumField(0xc0b20, 0xc82000a360)
/usr/local/go/src/reflect/type.go:660 +0x7b
我有两个结构体Person和Name：
type Person struct {
Fullname NameType
Sex string
}
type Name struct {
Firstname string
Lastname string
}
我在主函数中定义了Person，并使用递归函数显示结构体。
person := Person{
Name{"James", "Bound"},
"Male",
}
display(&person)
display函数递归显示结构体。
func display(s interface{}) {
reflectType := reflect.TypeOf(s).Elem()
reflectValue := reflect.ValueOf(s).Elem()
for i := 0; i < reflectType.NumField(); i++ {
typeName := reflectType.Field(i).Name
valueType := reflectValue.Field(i).Type()
valueValue := reflectValue.Field(i).Interface()
switch reflectValue.Field(i).Kind() {
case reflect.String:
fmt.Printf("%s : %s(%s)\n", typeName, valueValue, valueType)
case reflect.Int32:
fmt.Printf("%s : %i(%s)\n", typeName, valueValue, valueType)
case reflect.Struct:
fmt.Printf("%s : it is %s\n", typeName, valueType)
display(&valueValue)
}
}
}
英文:
I want to reflect the struct type and value recursively, but it fails. I don't know how to pass the sub struct recursively.
It error the following.
panic: reflect: NumField of non-struct type
goroutine 1 [running]:
reflect.(*rtype).NumField(0xc0b20, 0xc82000a360)
/usr/local/go/src/reflect/type.go:660 +0x7b
I have two struct Person and Name
type Person struct {
Fullname NameType
Sex string
}
type Name struct {
Firstname string
Lastname string
}
I define the Person in main, and display the struct with recursive function.
person := Person{
Name{"James", "Bound"},
"Male",
}
display(&person)
The display function recursive display the struct.
func display(s interface{}) {
reflectType := reflect.TypeOf(s).Elem()
reflectValue := reflect.ValueOf(s).Elem()
for i := 0; i < reflectType.NumField(); i++ {
typeName := reflectType.Field(i).Name
valueType := reflectValue.Field(i).Type()
valueValue := reflectValue.Field(i).Interface()
switch reflectValue.Field(i).Kind() {
case reflect.String:
fmt.Printf("%s : %s(%s)\n", typeName, valueValue, valueType)
case reflect.Int32:
fmt.Printf("%s : %i(%s)\n", typeName, valueValue, valueType)
case reflect.Struct:
fmt.Printf("%s : it is %s\n", typeName, valueType)
display(&valueValue)
}
}
}
答案1
得分: 7
在你的display函数内部，你声明了valueValue：
valueValue := reflectValue.Field(i).Interface()
所以valueValue的类型是interface{}。在for循环内部，你对display进行了递归调用：
display(&valueValue)
因此，它被调用时的参数类型是*interface{}。在递归调用内部，reflectType将表示interface{}而不是存储在值中的实际类型。由于NumField只能在表示结构体的reflect.Type上调用，所以会引发错误。
如果你想用指向结构体的指针调用display，你可以这样做：
v := valueValue := reflectValue.Field(i).Addr()
display(v.Interface())
英文:
Inside your display function, you declare valueValue as:
valueValue := reflectValue.Field(i).Interface()
So valueValue is of type interface{}. Inside the for loop, you have a recursive call to display:
display(&valueValue)
So it is being called with an argument of type *interface{}. Inside the recursive call, reflectType will represent interface{} rather than the type that happens to be stored within the value. Since NumField can only be called on reflect.Type's representing structs, you get a panic.
If you want to call display with a pointer to the struct instead, you could do so with something like this:
v := valueValue := reflectValue.Field(i).Addr()
display(v.Interface())
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