英文:
How can I tell if my interface{} is a pointer?
问题
如果我将一个接口传递给一个函数，有没有办法判断传入的项是一个结构体还是一个指向结构体的指针？我写了这个简单的测试来说明我需要解决的问题。
type MyStruct struct {
Value string
}
func TestInterfaceIsOrIsntPointer(t *testing.T) {
var myStruct interface{} = MyStruct{Value: "hello1"}
var myPointerToStruct interface{} = &MyStruct{Value: "hello1"}
// 接口上没有IsPointer方法，但我需要类似这样的方法
if myStruct.IsPointer() || !myPointerToStruct.IsPointer() {
t.Fatal("期望myStruct不是指针，而myPointerToStruct是指针")
}
}
英文:
If I have an interface being passed into a function, is there a way to tell if the item passed in is a struct or a pointer to a struct? I wrote this silly test to illustrate what I need to figure out.
type MyStruct struct {
Value string
}
func TestInterfaceIsOrIsntPointer(t *testing.T) {
var myStruct interface{} = MyStruct{Value: "hello1"}
var myPointerToStruct interface{} = &MyStruct{Value: "hello1"}
// the IsPointer method doesn't exist on interface, but I need something like this
if myStruct.IsPointer() || !myPointerToStruct.IsPointer() {
t.Fatal("expected myStruct to not be pointer and myPointerToStruct to be a pointer")
}
}
答案1
得分: 12
func isStruct(i interface{}) bool {
return reflect.ValueOf(i).Type().Kind() == reflect.Struct
}
你可以根据需要进行测试，例如更改类型为reflect.Ptr。在确保它是指针后，你甚至可以使用reflect.Indirect(reflect.ValueOf(i))获取指向的值。
补充：
看起来reflect.Value有一个Kind方法，所以reflect.ValueOf(i).Kind()就足够了。
英文:
func isStruct(i interface{}) bool {
return reflect.ValueOf(i).Type().Kind() == reflect.Struct
}
You can test via changing type according to your needs such as reflect.Ptr. You can even get pointed value with reflect.Indirect(reflect.ValueOf(i)) after you ensured it's a pointer.
Addition:
It seems reflect.Value has a Kind method so reflect.ValueOf(i).Kind() is enough.
答案2
得分: 3
你可以使用reflect包：
import (
"fmt"
"reflect"
)
func main() {
i := 42
j := &i
kindOfJ := reflect.ValueOf(j).Kind()
fmt.Print(kindOfJ == reflect.Ptr)
}
你可以使用reflect包来获取变量的类型信息。在上面的代码中，我们定义了一个整数变量i，然后使用&操作符获取了i的地址，并将其赋值给j。接下来，我们使用reflect.ValueOf()函数获取j的值的类型，并使用Kind()方法获取类型的种类。最后，我们将kindOfJ与reflect.Ptr进行比较，以确定j是否为指针类型。
英文:
You could use the reflect package:
i := 42
j := &i
kindOfJ := reflect.ValueOf(j).Kind()
fmt.Print(kindOfJ == reflect.Ptr)
答案3
得分: 2
如果你知道接口的“真实”类型，你可以简单地使用type switch：
type MyStruct struct {
Value string
}
func TestInterfaceIsOrIsntPointer(t *testing.T) {
var myStruct interface{} = MyStruct{Value: "hello1"}
var myPointerToStruct interface{} = &MyStruct{Value: "hello1"}
// 接口上没有IsPointer方法，但我需要类似这样的方法
switch myStruct.(type) {
case MyStruct:
// 正常
break
case *MyStruct:
// 这里有错误
break
}
switch myPointerToStruct.(type) {
case MyStruct:
// 这里有错误
break
case *MyStruct:
// 正常
break
}
}
这段代码更长，但至少你不需要使用reflect包。
英文:
If you know the "real" type of the interface, you can simply use a type switch:
type MyStruct struct {
Value string
}
func TestInterfaceIsOrIsntPointer(t *testing.T) {
var myStruct interface{} = MyStruct{Value: "hello1"}
var myPointerToStruct interface{} = &MyStruct{Value: "hello1"}
// the IsPointer method doesn't exist on interface, but I need something like this
switch myStruct.(type) {
case MyStruct:
// ok
break
case *MyStruct:
// error here
break
}
switch myPointerToStruct.(type) {
case MyStruct:
// error here
break
case *MyStruct:
// ok
break
}
}
The code is longer but at least you don't need to use the reflect package.
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