CODEWITHSUNDEEP
goprotocol-buffersgrpcgrpc-go
Danny
Danny

Reputation: 69

Converting internal go struct array to protobuf generated pointer array

I'm trying to convert an internal type to the protobuf generated type and I can't get the array to convert. I'm new to go so I don't know all the methods that could help. But this is my attempt. When run this code I get

panic: runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x86c724]

along with a lot other byte data. I'm wondering what the best way to convert internal structs to the protobufs is. I think I'm having the most trouble with the protobuf generated code being pointers.

Proto Definitions

message GameHistory {
  message Game {
    int64 gameId = 1;
  }

  repeated Game matches = 1;
  string username = 2;
}

message GetRequest {
  string username = 1;
}

message GetGameResponse {
  GameHistory gameHistory = 1;
}

Go Code

// GameHistory model
type GameHistory struct {
  Game []struct {
    GameID     int64  `json:"gameId"`
  } `json:"games"`
  UserName   string `json:"username"`
}

func constructGameHistoryResponse(gameHistory models.GameHistory) *pb.GetGameResponse {

  games := make([]*pb.GameHistory_Game, len(gameHistory.Games))
  for i := range matchHistory.Matches {
    games[i].GameID = gameHistory.Games[i].GameID
  }

  res := &pb.GetGameResponse{
    GameHistory: &pb.GameHistory{
      Games:    games,
    },
  }
}

Upvotes: 2

Views: 5111

Answers (1)

Brad
Brad

Reputation: 1128

Your games slice is initialized with nil values, as it's of type []*pb.GameHistory_Game (slice of pointers to pb.GameGistory_Game - init value for pointer is nil). You want to access the GameID property of those elements. You should create them instead :

for i := range matchHistory.Matches {
    games[i]=&pb.GameHistory{GameID: gameHistory.Games[i].GameID}
}

Also, I recommend taking a look over the go protobuf documentation, as you have the Marshal and Unmarshal methods there for decoding and encoding protobuf messages.

Upvotes: 3

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