英文:
How to correctly determine the type of variable google.protobuf.Any?
问题
请告诉我这段代码中有什么问题，为什么变量的类型无法确定，传递的url类型是google.protobuf.Any？
package main
import (
"fmt"
"google.golang.org/protobuf/reflect/protoreflect"
"google.golang.org/protobuf/reflect/protoregistry"
)
func main() {
var res protoregistry.MessageTypeResolver = protoregistry.GlobalTypes
typeUrl := "type.googleapis.com/google.protobuf.StringValue"
fmt.Println(protoreflect.FullName(typeUrl))
msgType, err := protoregistry.GlobalTypes.FindMessageByName(protoreflect.FullName("google.protobuf.StringValue"))
if err != nil {
fmt.Println(err)
}
fmt.Println(msgType)
msgType, err = res.FindMessageByURL(typeUrl)
if err != nil {
fmt.Println(err)
}
fmt.Println(msgType)
}
proto: not found
proto: not found
英文:
Please tell me what is wrong in this code, why the type is not determined for the variable, for the transmitted url type google.protobuf.Any?
package main
import (
"fmt"
"google.golang.org/protobuf/reflect/protoreflect"
"google.golang.org/protobuf/reflect/protoregistry"
)
func main() {
var res protoregistry.MessageTypeResolver = protoregistry.GlobalTypes
typeUrl := "type.googleapis.com/google.protobuf.StringValue"
fmt.Println(protoreflect.FullName(typeUrl))
msgType, err := protoregistry.GlobalTypes.FindMessageByName(protoreflect.FullName("google.protobuf.StringValue"))
if err != nil {
fmt.Println(err)
}
fmt.Println(msgType)
msgType, err = res.FindMessageByURL(typeUrl)
if err != nil {
fmt.Println(err)
}
fmt.Println(msgType)
}
proto: not found
<nil>
proto: not found
<nil>
答案1
得分: 1
错误是protoregistry.NotFound，因为在protoregistry.GlobalTypes中没有注册消息类型。
要注册google.protobuf.Any，您应该导入包google.golang.org/protobuf/types/known/anypb。并且google.protobuf.Any是由该包的init函数注册的（请参阅源代码）。
要注册google.protobuf.StringValue，您应该导入包google.golang.org/protobuf/types/known/wrapperspb。
这是更新后的演示代码，用于查找google.protobuf.StringValue的消息字节：
package main
import (
"fmt"
"google.golang.org/protobuf/reflect/protoregistry"
// 仅导入该包以产生副作用（初始化）。
// 请参阅https://go.dev/ref/spec#Import_declarations。
_ "google.golang.org/protobuf/types/known/anypb"
_ "google.golang.org/protobuf/types/known/wrapperspb"
)
func main() {
res := protoregistry.GlobalTypes
fmt.Println("NumMessages:", res.NumMessages())
msgType, err := protoregistry.GlobalTypes.FindMessageByName("google.protobuf.StringValue")
if err != nil {
fmt.Println(err)
}
fmt.Println(msgType)
msgType, err = res.FindMessageByURL("type.googleapis.com/google.protobuf.StringValue")
if err != nil {
fmt.Println(err)
}
fmt.Println(msgType)
}
英文:
The error is protoregistry.NotFound because there are not message types got registered in protoregistry.GlobalTypes.
To register google.protobuf.Any, you should import the package google.golang.org/protobuf/types/known/anypb. And google.protobuf.Any is registered by the init function of that package (see the source code).
To register google.protobuf.StringValue, you should import the package google.golang.org/protobuf/types/known/wrapperspb.
Here is the updated demo that finds the message byte of google.protobuf.StringValue:
package main
import (
"fmt"
"google.golang.org/protobuf/reflect/protoregistry"
// importing the package solely for its side-effects (initialization).
// See https://go.dev/ref/spec#Import_declarations.
_ "google.golang.org/protobuf/types/known/anypb"
_ "google.golang.org/protobuf/types/known/wrapperspb"
)
func main() {
res := protoregistry.GlobalTypes
fmt.Println("NumMessages:", res.NumMessages())
msgType, err := protoregistry.GlobalTypes.FindMessageByName("google.protobuf.StringValue")
if err != nil {
fmt.Println(err)
}
fmt.Println(msgType)
msgType, err = res.FindMessageByURL("type.googleapis.com/google.protobuf.StringValue")
if err != nil {
fmt.Println(err)
}
fmt.Println(msgType)
}
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