Go 代码生成指南（不透明）

go install google.golang.org/protobuf/cmd/protoc-gen-go@latest

protoc --proto_path=src --go_out=out --go_opt=paths=source_relative foo.proto bar/baz.proto

option go_package = "example.com/project/protos/fizz";

protoc --proto_path=src \
  --go_opt=Mprotos/buzz.proto=example.com/project/protos/fizz \
  --go_opt=Mprotos/bar.proto=example.com/project/protos/foo \
  protos/buzz.proto protos/bar.proto

edition = "2023";

package log;

import "google/protobuf/go_features.proto";
option features.(pb.go).api_level = API_OPAQUE;

message LogEntry { … }

protoc […] --go_opt=default_api_level=API_HYBRID

protoc […] --go_opt=apilevelMhello.proto=API_HYBRID

message Artist {}

message Artist {
  message Name {
  }
}

optional int32 birth_year = 1;
required int32 birth_year = 1;

func (m *Artist) GetBirthYear() int32 { ... }
func (m *Artist) SetBirthYear(v int32) { ... }
func (m *Artist) HasBirthYear() bool { ... }
func (m *Artist) ClearBirthYear() { ... }

int32 birth_year = 1;
optional int32 first_active_year = 2;

func (m *Artist) GetBirthYear() int32 { ... }
func (m *Artist) SetBirthYear(v int32) { ... }
// NOTE: No HasBirthYear() or ClearBirthYear() methods;
// proto3 fields only have presence when declared as optional:
// /programming-guides/field_presence.md

func (m *Artist) GetFirstActiveYear() int32 { ... }
func (m *Artist) SetFirstActiveYear(v int32) { ... }
func (m *Artist) HasFirstActiveYear() bool { ... }
func (m *Artist) ClearFirstActiveYear() { ... }

message Band {}

// proto2
message Concert {
  optional Band headliner = 1;
  // The generated code is the same result if required instead of optional.
}

// proto3
message Concert {
  Band headliner = 1;
}

type Concert struct { ... }

func (m *Concert) GetHeadliner() *Band { ... }
func (m *Concert) SetHeadliner(v *Band) { ... }
func (m *Concert) HasHeadliner() bool { ... }
func (m *Concert) ClearHeadliner() { ... }

var m *Concert // defaults to nil
log.Infof("GetFoundingYear() = %d (no panic!)", m.GetHeadliner().GetFoundingYear())

message Concert {
  // Best practice: use pluralized names for repeated fields:
  // /programming-guides/style#repeated-fields
  repeated Band support_acts = 1;
}

type Concert struct { ... }

func (m *Concert) GetSupportActs() []*Band { ... }
func (m *Concert) SetSupportActs(v []*Band) { ... }

concert := Concert_builder{
  SupportActs: []*Band{
    {}, // First element.
    {}, // Second element.
  },
}.Build()

concert := &Concert{}
concert.SetSupportActs([]*Band{
    {}, // First element.
    {}, // Second element.
})

support := concert.GetSupportActs() // support type is []*Band.
b1 := support[0] // b1 type is *Band, the first element in support_acts.

message MerchItem {}

message MerchBooth {
  // items maps from merchandise item name ("Signed T-Shirt") to
  // a MerchItem message with more details about the item.
  map<string, MerchItem> items = 1;
}

type MerchBooth struct { ... }

func (m *MerchBooth) GetItems() map[string]*MerchItem { ... }
func (m *MerchBooth) SetItems(v map[string]*MerchItem) { ... }

package account;
message Profile {
  oneof avatar {
    string image_url = 1;
    bytes image_data = 2;
  }
}

type Profile struct { ... }

func (m *Profile) WhichAvatar() case_Profile_Avatar { ... }
func (m *Profile) GetImageUrl() string { ... }
func (m *Profile) GetImageData() []byte { ... }

func (m *Profile) SetImageUrl(v string) { ... }
func (m *Profile) SetImageData(v []byte) { ... }

func (m *Profile) HasAvatar() bool { ... }
func (m *Profile) HasImageUrl() bool { ... }
func (m *Profile) HasImageData() bool { ... }

func (m *Profile) ClearAvatar() { ... }
func (m *Profile) ClearImageUrl() { ... }
func (m *Profile) ClearImageData() { ... }

p1 := accountpb.Profile_builder{
  ImageUrl: proto.String("https://example.com/image.png"),
}.Build()

// imageData is []byte
imageData := getImageData()
p2 := &accountpb.Profile{}
p2.SetImageData(imageData)

switch m.WhichAvatar() {
case accountpb.Profile_ImageUrl_case:
    // Load profile image based on URL
    // using m.GetImageUrl()

case accountpb.Profile_ImageData_case:
    // Load profile image based on bytes
    // using m.GetImageData()

case accountpb.Profile_Avatar_not_set_case:
    // The field is not set.

default:
    return fmt.Errorf("Profile.Avatar has an unexpected new oneof field %v", x)
}

message Venue {
  enum Kind {
    KIND_UNSPECIFIED = 0;
    KIND_CONCERT_HALL = 1;
    KIND_STADIUM = 2;
    KIND_BAR = 3;
    KIND_OPEN_AIR_FESTIVAL = 4;
  }
  Kind kind = 1;
  // ...
}

type Venue_Kind int32

const (
    Venue_KIND_UNSPECIFIED       Venue_Kind = 0
    Venue_KIND_CONCERT_HALL      Venue_Kind = 1
    Venue_KIND_STADIUM           Venue_Kind = 2
    Venue_KIND_BAR               Venue_Kind = 3
    Venue_KIND_OPEN_AIR_FESTIVAL Venue_Kind = 4
)

type Venue_Kind int32

enum Genre {
  GENRE_UNSPECIFIED = 0;
  GENRE_ROCK = 1;
  GENRE_INDIE = 2;
  GENRE_DRUM_AND_BASS = 3;
  // ...
}

type Genre int32

func (Genre) Enum() *Genre

const (
    Venue_KIND_UNSPECIFIED       Venue_Kind = 0
    Venue_KIND_CONCERT_HALL      Venue_Kind = 1
    Venue_KIND_STADIUM           Venue_Kind = 2
    Venue_KIND_BAR               Venue_Kind = 3
    Venue_KIND_OPEN_AIR_FESTIVAL Venue_Kind = 4
)

const (
    Genre_GENRE_UNSPECIFIED   Genre = 0
    Genre_GENRE_ROCK          Genre = 1
    Genre_GENRE_INDIE         Genre = 2
    Genre_GENRE_DRUM_AND_BASS Genre = 3
)

var Genre_name = map[int32]string{
    0: "GENRE_UNSPECIFIED",
    1: "GENRE_ROCK",
    2: "GENRE_INDIE",
    3: "GENRE_DRUM_AND_BASS",
}
var Genre_value = map[string]int32{
    "GENRE_UNSPECIFIED":   0,
    "GENRE_ROCK":          1,
    "GENRE_INDIE":         2,
    "GENRE_DRUM_AND_BASS": 3,
}

extend Concert {
  optional int32 promo_id = 123;
}

extend Concert {
  optional int32 singular_int32 = 1;
  repeated bytes repeated_strings = 2;
  optional Band singular_message = 3;
}

m := &somepb.Concert{}
proto.SetExtension(m, extpb.E_SingularInt32, int32(1))
proto.SetExtension(m, extpb.E_RepeatedString, []string{"a", "b", "c"})
proto.SetExtension(m, extpb.E_SingularMessage, &extpb.Band{})

v1 := proto.GetExtension(m, extpb.E_SingularInt32).(int32)
v2 := proto.GetExtension(m, extpb.E_RepeatedString).([][]byte)
v3 := proto.GetExtension(m, extpb.E_SingularMessage).(*extpb.Band)

message Promo {
  extend Concert {
    optional int32 promo_id = 124;
  }
}