Using promises in React Native modules with Swift

README.md

Instructions

• In a new or existing project called MyProject (for example) add the .h, .m and .swift files to the /ios/ directory
• Put the ReactNativeSwiftPromises file wherever you like
• Launch/compile your react native project. Note: whenever you change the native files you'll need to recompile with XCode

NOTE: if this example doesn't compile/work let me know. I just pasted random bits from a project without checking if it compiles. I'm using 9.2 with RN 0.55.2

Login.m

//  Created by react-native-create-bridge

// import RCTBridgeModule
#if __has_include(<React/RCTBridgeModule.h>)
#import <React/RCTBridgeModule.h>
#elif __has_include(“RCTBridgeModule.h”)
#import “RCTBridgeModule.h”
#else
#import “React/RCTBridgeModule.h” // Required when used as a Pod in a Swift project
#endif

// import RCTEventEmitter
#if __has_include(<React/RCTEventEmitter.h>)
#import <React/RCTEventEmitter.h>
#elif __has_include(“RCTEventEmitter.h”)
#import “RCTEventEmitter.h”
#else
#import “React/RCTEventEmitter.h” // Required when used as a Pod in a Swift project
#endif

// Export a native module
// https://facebook.github.io/react-native/docs/native-modules-ios.html#exporting-swift
@interface RCT_EXTERN_MODULE(Login, NSObject)

// Export methods to a native module
// https://facebook.github.io/react-native/docs/native-modules-ios.html#exporting-swift
RCT_EXTERN_METHOD(
                  login: (NSString *)email
                  password:(NSString *)password
                  resolve: (RCTPromiseResolveBlock)resolve
                  rejecter:(RCTPromiseRejectBlock)reject
                  )

@end

Login.swift

//  Created by react-native-create-bridge

import Foundation

@objc(Login)
class PromiseTest : NSObject { 
  @objc
  func login(_ email: String, password: String, resolve: RCTPromiseResolveBlock, rejecter reject: RCTPromiseRejectBlock) -> Void {
    resolve("You sent: email '\(email)', password '\(password)'")
  }
}

MyProject-Bridging-Header.h

// This enables the Swift file to be used with RN. If you were just using ObjC you wouldn't need this

//  Created by react-native-create-bridge
// PromiseTest-Bridging-Header.h

// import RCTBridgeModule
#if __has_include(<React/RCTBridgeModule.h>)
#import <React/RCTBridgeModule.h>
#elif __has_include(“RCTBridgeModule.h”)
#import “RCTBridgeModule.h”
#else
#import “React/RCTBridgeModule.h” // Required when used as a Pod in a Swift project
#endif

// import RCTEventEmitter
#if __has_include(<React/RCTEventEmitter.h>)
#import <React/RCTEventEmitter.h>
#elif __has_include(“RCTEventEmitter.h”)
#import “RCTEventEmitter.h”
#else
#import “React/RCTEventEmitter.h” // Required when used as a Pod in a Swift project
#endif

ReactNativeSwiftPromises.js

import React from "react";
import { StyleSheet, Text, View, Button } from "react-native";

import { NativeModules } from "react-native";

const { Login } = NativeModules;

const login = async () => {
  const response = await PromiseTest.login("Bob", "Salmon");
  console.log(respone); // "You sent: email Bob, password Salmon"
};

export default class App extends React.Component {
  render() {
    return (
      <View style={styles.container}>
        <Text>Press button to log in</Text>
        <Button onPress={login} title="Login" />
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: "#fff",
    alignItems: "center",
    justifyContent: "center",
  },
});

Got some questions regarding the threading. Let's assume the login method makes a network request, and calls a closure (not necessarily on the main thread). Is it still safe to call the resolve or reject in that closure? How would that work?

I am having this error, could someone help me?

I am having this error, could someone help me?

Add import React

@bxvd you will need to create a bridging header file with the following import
#import <React/RCTBridgeModule.h>

It'd be good to have an example of how to use the rejecter:

reject("failed_login", "Failed to log in", error)

It takes three parameters: an identifier, message, and error object if I understand correctly.