It's been a long time since I updated my blog. On the one hand, I have been busy with internships and there are really a lot of things waiting for me to learn, which is terrifying. On the other hand, I'm just lazy
Protobuf is really a good thing, but it's a bit tricky to get the value of a specific field when you don't know the exact structure. After a lot of tinkering, I finally figured it out. I'll write a blog post to record it.
func FindByName(name string, msg protoreflect.Message) (has bool, value protoreflect.Value, isList bool) {
if name == "" {
return false, *new(protoreflect.Value), false
}
msgDesc := msg.Descriptor()
for i := 0; i < msgDesc.Fields().Len(); i++ {
if msgDesc.Fields().Get(i).Kind() == protoreflect.MessageKind {
sonMsg := msgDesc.Fields().Get(i)
has, value, isList = FindByName(name, msg.Get(sonMsg).Message()) // type mismatch: cannot convert list to message
if has {
return has, value, isList
}
}
if msgDesc.Fields().Get(i).Name() == protoreflect.Name(name) {
return true, msg.Get(msgDesc.Fields().Get(i)), msgDesc.Fields().Get(i).IsList()
}
}
return false, value, false
}
This also takes into account the case where a message is nested inside a proto message, for reference only.
update:
There is a small pitfall. If the field is a slice, according to the source code, the interface obtained using the Interface() function is a pointer to this slice, and the type obtained through reflection is Ptr, which makes the subsequent processing a bit tricky. So I directly added a check inside the function to determine whether it is of List type, and return the corresponding processing based on the boolean value.
func (v Value) Interface() interface{} {
switch v.typ {
case nilType:
return nil
case boolType:
return v.Bool()
case int32Type:
return int32(v.Int())
case int64Type:
return int64(v.Int())
case uint32Type:
return uint32(v.Uint())
case uint64Type:
return uint64(v.Uint())
case float32Type:
return float32(v.Float())
case float64Type:
return float64(v.Float())
case stringType:
return v.String()
case bytesType:
return v.Bytes()
case enumType:
return v.Enum()
default:
return v.getIface()
}
}
func (v Value) getIface() (x interface{}) {
*(*ifaceHeader)(unsafe.Pointer(&x)) = ifaceHeader{Type: v.typ, Data: v.ptr}
return x
}