React Native gRPC Swift/Java bridge generator

If you are developing React Native app and using gRPC for backend communication when you need to bind native gRPC Swift/Android packages and communicate between native and javascript. React Native accepts only Dictionaries and Arrays with primitive types.

Features

• Generate Swift Unary calls code for JS mappings
• Generate iOS Swift bridge header
• Generate Typescript interfaces for JS/TS
• Generate Swift Streaming calls code for JS mappings
• Generate Android Unary code for JS mappings
• Generate Android Streaming code for JS mappings

Example Use case

1. Lets say we have proto

message Book {
    int64 isbn = 1;
    string title = 2;
    string author = 3;
    int32 pages = 4;
    bool isActivate = 5;
    BookDetails details = 6;
}

message GetTypesRequest {
    double dbl = 1;
    float flt = 2;
    int32 intr32 = 3;
    int64 intr64 = 4;
    uint32 uintr32 = 5;
    uint64 uintr64 = 6;
    sint32 suint32 = 7;
    sint64 suint64 = 8;
    fixed32	fxd32 = 9;
    fixed64	fxd64 = 10;
    sfixed32 sfxd32 = 11;
    sfixed64 sfxd64 = 12;
    bool bln = 13;
    string str = 14;
    bytes bytx = 15;
    repeated Book books = 16;
    Book book = 17;
}

message GetTypesResponse {
    double dbl = 1;
    float flt = 2;
    int32 intr32 = 3;
    int64 intr64 = 4;
    uint32 uintr32 = 5;
    uint64 uintr64 = 6;
    sint32 suint32 = 7;
    sint64 suint64 = 8;
    fixed32	fxd32 = 9;
    fixed64	fxd64 = 10;
    sfixed32 sfxd32 = 11;
    sfixed64 sfxd64 = 12;
    bool bln = 13;
    string str = 14;
    bytes bytx = 15;
    repeated Book books = 16;
    Book book = 17;
}

service BookService {
    rpc GetTypes (GetTypesRequest) returns (GetTypesResponse) {}
}

2. Now if you want to call GetTypes method from javascript you need to write all these mappings

@objc(BookService)
class BookService: NSObject, GrpcService {

  @objc func GetTypes(_ req$: [String: Any], resolve: RCTPromiseResolveBlock, reject: RCTPromiseRejectBlock) -> Void {
    let svc = BookServiceClient()
    var req = Book_GetTypesRequest()

    // request mapping
    req.dbl = req$["dbl"] as? Double ?? 0
    req.flt = req$["flt"] as? Float ?? 0
    req.intr32 = Int32(req$["intr32"] as? Int ?? 0)
    req.intr64 = Int64(req$["intr64"] as? Int ?? 0)
    req.uintr32 = UInt32(req$["uintr32"] as? Int ?? 0)
    req.uintr64 = UInt64(req$["uintr64"] as? Int ?? 0)
    req.suint32 = Int32(req$["suint32"] as? Int ?? 0)
    req.suint64 = Int64(req$["suint64"] as? Int ?? 0)
    req.fxd32 = UInt32(req$["fxd32"] as? Int ?? 0)
    req.fxd64 = UInt64(req$["fxd64"] as? Int ?? 0)
    req.sfxd32 = Int32(req$["sfxd32"] as? Int ?? 0)
    req.sfxd64 = Int64(req$["sfxd64"] as? Int ?? 0)
    req.bln = req$["bln"] as? Bool ?? false
    req.str = req$["str"] as? String ?? ""
    req.bytx = req$["bytx"] as? Data ?? Data()
    if let arr = req$["books"] as? [[String: Any]] {
      for item in arr {
        if let books_Book$ = item as? [String: Any] {
          var books_Book = Book()
          books_Book.isbn = Int64(books_Book$["isbn"] as? Int ?? 0)
          books_Book.title = books_Book$["title"] as? String ?? ""
          books_Book.author = books_Book$["author"] as? String ?? ""
          books_Book.pages = Int32(books_Book$["pages"] as? Int ?? 0)
          books_Book.isActivate = books_Book$["isActivate"] as? Bool ?? false
          if let details_BookDetails$ = books_Book$["details"] as? [String: Any] {
            var details_BookDetails = BookDetails()
            details_BookDetails.pages = Int32(details_BookDetails$["pages"] as? Int ?? 0)
            books_Book.details = details_BookDetails
          }
          req.books.append(books_Book)
        }
      }
    }
    if let book_Book$ = item["book"] as? [String: Any] {
      var book_Book = Book()
      book_Book.isbn = Int64(book_Book$["isbn"] as? Int ?? 0)
      book_Book.title = book_Book$["title"] as? String ?? ""
      book_Book.author = book_Book$["author"] as? String ?? ""
      book_Book.pages = Int32(book_Book$["pages"] as? Int ?? 0)
      book_Book.isActivate = book_Book$["isActivate"] as? Bool ?? false
      if let details_BookDetails$ = book_Book$["details"] as? [String: Any] {
        var details_BookDetails = BookDetails()
        details_BookDetails.pages = Int32(details_BookDetails$["pages"] as? Int ?? 0)
        book_Book.details = details_BookDetails
      }
      req.book = book_Book
    }
    // end request mapping

    do {
      let res = try svc.GetTypes(req)
      var res$: [String: Any] = [:]

      // response mapping
      res$["dbl"] = res.dbl
      res$["flt"] = res.flt
      res$["intr32"] = res.intr32
      res$["intr64"] = res.intr64
      res$["uintr32"] = res.uintr32
      res$["uintr64"] = res.uintr64
      res$["suint32"] = res.suint32
      res$["suint64"] = res.suint64
      res$["fxd32"] = res.fxd32
      res$["fxd64"] = res.fxd64
      res$["sfxd32"] = res.sfxd32
      res$["sfxd64"] = res.sfxd64
      res$["bln"] = res.bln
      res$["str"] = res.str
      res$["bytx"] = res.bytx
      var books$: [[String: Any]] = []
      for item in res.books {
        var _books_Book = item
        var _books_Book$: [String: Any] = [:]
        _books_Book$["isbn"] = _books_Book.isbn
        _books_Book$["title"] = _books_Book.title
        _books_Book$["author"] = _books_Book.author
        _books_Book$["pages"] = _books_Book.pages
        _books_Book$["isActivate"] = _books_Book.isActivate
        var _details_BookDetails = _books_Book.details
        var _details_BookDetails$: [String: Any] = [:]
        _details_BookDetails$["pages"] = _details_BookDetails.pages
        _books_Book$["details"] = _details_BookDetails$
        books$.append(_books_Book$)
      }
      res$["books"] = books$
      var _book_Book = res.book
      var _book_Book$: [String: Any] = [:]
      _book_Book$["isbn"] = _book_Book.isbn
      _book_Book$["title"] = _book_Book.title
      _book_Book$["author"] = _book_Book.author
      _book_Book$["pages"] = _book_Book.pages
      _book_Book$["isActivate"] = _book_Book.isActivate
      var _details_BookDetails = _book_Book.details
      var _details_BookDetails$: [String: Any] = [:]
      _details_BookDetails$["pages"] = _details_BookDetails.pages
      _book_Book$["details"] = _details_BookDetails$
      res$["book"] = _book_Book$
      // end response mapping

      resolve(res$)
    } catch {
      reject("ERROR", error.localizedDescription, error)
    }
  }
}

3. rn-grpc-bridge generator can do it for you

Usage

1. Install

yarn add rn-grpc-bridge --dev

2. Compile using protoc compiler

protoc \
--rn_out=${OUTDIR} \
--plugin=protoc-gen-rn=./node_modules/.bin/rn-grpc-bridge \
-I ./proto \
proto/*.proto

3. Initialize services from react native. See generate grpc_config.swift for call arguments.

import { NativeModules, DebugService } from 'react-native';
import { DebugService, PingRequest } from './pb/debug_grpc_pb_types';

// inside some initial component
class InitialScreen {
  async componentDidMount() {
    const grpcConfig = NativeModules.GrpcConfig;

    // init for local dev
    await grpcConfig.initServices('localhost:9000', false, '');
    // or for secure with TLS cert to staging/prod
    // await grpcConfig.initServices('corp.staging.com', true, 'certname');

    // it is also possible to set global for all services metadata
    await grpcConfig.setMetadata({
      'x-key': 'x-value',
      'api-key': 'abc1'
    });

    // now we are ready to call grpc
    const debugService: DebugService = NativeModules.DebugService;
    const req: PingRequest = {
      message: `ping from react native ${new Date().getTime()}`
    };
    const rsp = await debugService.ping(req);
    console.log(rsp);
  }
}

Docker

See example which uses Docker image to run rn-grpc-bridge without any external library.