[英]Get all fields from an interface
How do I know the fields I can access from the reply
object/interface? 如何知道我可以从reply
对象/界面访问的字段? I tried reflection but it seems you have to know the field name first. 我尝试过反射,但似乎你必须首先知道字段名称。 What if I need to know all the fields available to me? 如果我需要知道可用的所有字段怎么办?
// Do sends a command to the server and returns the received reply.
Do(commandName string, args ...interface{}) (reply interface{}, err error)
You can use the reflect.TypeOf()
function to obtain a reflect.Type
type descriptor. 您可以使用reflect.TypeOf()
函数来获取reflect.Type
类型描述符。 From there, you can list fields of the dynamic value stored in the interface. 从那里,您可以列出存储在界面中的动态值的字段。
Example: 例:
type Point struct {
X int
Y int
}
var reply interface{} = Point{1, 2}
t := reflect.TypeOf(reply)
for i := 0; i < t.NumField(); i++ {
fmt.Printf("%+v\n", t.Field(i))
}
Output: 输出:
{Name:X PkgPath: Type:int Tag: Offset:0 Index:[0] Anonymous:false}
{Name:Y PkgPath: Type:int Tag: Offset:4 Index:[1] Anonymous:false}
The result of a Type.Field()
call is a reflect.StructField
value which is a struct
, containing the name of the field among other things: Type.Field()
调用的结果是一个reflect.StructField
值,它是一个struct
,包含字段的名称以及其他内容:
type StructField struct {
// Name is the field name.
Name string
// ...
}
If you also want the values of the fields, you may use reflect.ValueOf()
to obtain a reflect.Value()
, and then you may use Value.Field()
or Value.FieldByName()
: 如果您还想要字段的值,可以使用reflect.ValueOf()
来获取reflect.Value()
,然后您可以使用Value.Field()
或Value.FieldByName()
:
v := reflect.ValueOf(reply)
for i := 0; i < v.NumField(); i++ {
fmt.Println(v.Field(i))
}
Output: 输出:
1
2
Try it on the Go Playground . 在Go Playground尝试一下。
Note: often a pointer to struct is wrapped in an interface. 注意:通常指向struct的指针包含在接口中。 In such cases you may use Type.Elem()
and Value.Elem()
to "navigate" to the pointed type or value: 在这种情况下,您可以使用Type.Elem()
和Value.Elem()
来“导航”到指向的类型或值:
t := reflect.TypeOf(reply).Elem()
v := reflect.ValueOf(reply).Elem()
If you don't know whether it's a pointer or not, you can check it with Type.Kind()
and Value.Kind()
, comparing the result with reflect.Ptr
: 如果您不知道它是否是指针,可以使用Type.Kind()
和Value.Kind()
进行检查,并将结果与reflect.Ptr
进行比较:
t := reflect.TypeOf(reply)
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
// ...
v := reflect.ValueOf(reply)
if v.Kind() == reflect.Ptr {
v = v.Elem()
}
Try this variant on the Go Playground . 在Go Playground上试试这个变种。
For a detailed introduction to Go's reflection, read the blog post: The Laws of Reflection . 有关Go的反思的详细介绍,请阅读博客文章: 反思的法则 。
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