Swift NativeModule for iOS is always null

Question

I am building a mobile application using ReactNative for both IOS and Android. I am also building a native module for iOS using Swift. But when I access the module class from JS, it is always returning null.

I created a WaterRowerBleManager.swift file with the following code.

import Foundation

@objc(WaterRowerBleManager)
class WaterRowerBleManager: NSObject {
  @objc
  func constantsToExpose() -> [AnyHashable : Any]! {
    return [
          "number": 123.9,
          "string": "foo",
          "boolean": true,
          "array": [1, 22.2, "33"],
          "object": ["a": 1, "b": 2]
        ]
  }
  
  @objc
  static func requiresMainQueueSetup() -> Bool {
     return true
  }
}

It created a bridge header file with the ".h" extension as well. I have left the file as is.

Then I created a WaterRowerBleManager.m file with the following code.

#import <Foundation/Foundation.h>
#import "React/RCTBridgeModule.h"

@interface RCT_EXTERN_MODULE(WaterRowerBleManager, NSObject)
@end

From the ReactNative, in access the module from App.js as follow.

import { NativeModules } from 'react-native';
NativeModules.WaterRowerBleManager

The NativeModules.WaterRowerBleManager is always returning null. What is wrong with my code and how can I fix it?

Have you added the import statement in the WaterRowerBleManager-Bridging-Header.h file? — Jignesh Mayani, Jul 14 '21 at 11:19
I put in this #import "React/RCTBridgeModule.h" . Do I need to add something else? @JigneshMayani? — Wai Yan Hein, Jul 14 '21 at 11:21
@SunnyShah, I don't think so. Which file should I put it in? — Wai Yan Hein, Jul 14 '21 at 12:50

score 1 · Accepted Answer · answered Jul 14 '21 at 13:05

1

You need to create Bridge file and need to export module name to use it.

in your WaterRowerBleManager.h File

#import <React/RCTBridgeModule.h>

@interface WaterRowerBleManager : NSObject @end

in your WaterRowerBleManager.m File

RCT_EXPORT_MODULE(WaterRowerBleManager);

answered Jul 14 '21 at 13:05

Sunny Shah

12,990
9
50
86

It is complaing mising context for method declaration when I add that in. – Wai Yan Hein Jul 14 '21 at 13:28

score 1 · Answer 2 · answered Jan 13 '22 at 18:47

1

Met the same problem here. Found the main reason is that ReactNative will not load your NativeModule if you did not expose any method in it. So the solution is to capsule some methods in .m and rebuild/reload.

answered Jan 13 '22 at 18:47

Wu Tora

11
1

Swift NativeModule for iOS is always null

2 Answers2