Marshall/Unmarshal JSONPB - go

Question

I am trying to Unmarshal some json data to a proto message.
JSON
{
"id": 1,
"first_name": "name",
"phone_numbers": []
}
Proto
message Item {
uint32 id=1;
string name=2;
repeated string numbers=3;
}
Proto.go
type Item struct {
Id uint32 `protobuf:"varint,1,opt,name=id" json:"id,omitempty"`
Name string `protobuf:"bytes,2,opt,name=name" json:"name,omitempty"`
Numbers []string `protobuf:"bytes,4,rep,name=numbers" json:"numbers,omitempty"`
}
How can I map the above JSON to my proto Message (from what I can see there is no way to specify tags in proto atm)?

Answer 1

Your JSON document doesn't match the proto definition; name != first_name and numbers != phone_numbers.
You can define another type that has the same fields as Item but different struct tags and then convert to Item:
var x struct {
Id uint32 `json:"id,omitempty"`
Name string `json:"first_name,omitempty"`
Numbers []string `json:"phone_numbers,omitempty"`
}
if err := json.Unmarshal(jsonDoc, &x); err != nil {
log.Fatal(err)
}
var i = Item(x)
If every JSON document you want to decode has this structure, it may be more convenient to let Item implement json.Unmarshaler:
package main
import (
"encoding/json"
"fmt"
"log"
)
var jsonDoc = []byte(`
{
"id": 1,
"first_name": "name",
"phone_numbers": [
"555"
]
}
`)
type Item struct {
Id uint32 `protobuf:"varint,1,opt,name=id" json:"id,omitempty"`
Name string `protobuf:"bytes,2,opt,name=name" json:"name,omitempty"`
Numbers []string `protobuf:"bytes,4,rep,name=numbers" json:"numbers,omitempty"`
}
// You can define this function is item_json.go or so, then it
// isn't removed if you re-generate your types.
func (i *Item) UnmarshalJSON(b []byte) error {
type item struct {
Id uint32 `json:"id,omitempty"`
Name string `json:"first_name,omitempty"`
Numbers []string `json:"phone_numbers,omitempty"`
}
var x item
if err := json.Unmarshal(jsonDoc, &x); err != nil {
return err
}
*i = Item(x)
return nil
}
func main() {
var i Item
if err := json.Unmarshal(jsonDoc, &i); err != nil {
log.Fatal(err)
}
fmt.Printf("%#v\n", i)
}
Try it on the playground: https://play.golang.org/p/0qibavRJbwi