component.js

import React from 'react';
import { NativeModules } from 'react-native';

const { MyModule } = NativeModules;

class MyComponent extends React.Component {

componentDidMount() {
  loadData();
}

async loadData() {
  try {
    var products = await MyModule.loadProducts(this.props.orderId);
    // do something with products
  } catch (e) {
    console.error(e);
  }
}

MyModule.swift

import Foundation
import React

@objc(MyModule)
class MyModule: RCTEventEmitter {
        
  @objc func loadProducts(_ orderId: NSNumber, resolve: RCTPromiseResolveBlock, reject: RCTPromiseRejectBlock) {
    let products = // load products somehow ...
    if products {
      resolve(products);
    } else {
      reject(errorCode, errorMessage, error);
    }
}

MyModuleBridge.m

@import Foundation;
#import "RCTBridgeModule.h"

@interface RCT_EXTERN_MODULE(MyModule, NSObject)

RCT_EXTERN_METHOD(loadProducts:(nonnull NSNumber *)orderId 
                       resolve:(RCTPromiseResolveBlock)resolve 
                        reject:(RCTPromiseRejectBlock)reject)

@end