Cordova-plugin-iosrtc: Getting : TypeError: undefined is not an object (evaluating 'stream.id') when removing a shared screen

[magestican]

Whenever i remove a shared screen stream on chrome in windows, i get this exception on my ios app built with iosrtc :

callbackFromNative — cordova.js:314 TypeError: undefined is not an object (evaluating 'stream.id').

I have gone through the source code and there are 3 or 4 situations when source.id is being used by iosrtc, could a check be added anywhere stream.id is being used so this doesnt happen?

[ibc]

I have gone through the source code and there are 3 or 4 situations when source.id is being used by iosrtc, could a check be added anywhere stream.id is being used so this doesnt happen?

I think it's better to find out why the error happens (rather than just checking conditions with no knowledge of why they could fail). BTW: have you identified the exact line in which such a stream.id fails?

[saghul]

Agreed with @ibc here. Adding a check is a stopgap at best.

[justindujardin]

We've run into this issue as well, I can elaborate. The use-case is a long-lived peer connection where remote streams are frequently added/removed. On removal the stream is not found in remoteStreams, and an exception is generated when stream.id is used.

The root cause appears to be #164 where a unique ID was added to the stream ids that are tracked internally. The generated ids are not properly communicated to the javascript layer, and so the cleanup logic fails when a remote stream is removed.

We originally tried removing the unique IDs because we don't use Kurento, but this resulted in some media failures, so I later patched the javascript to look for a substring match. This works fine because we generate unique ids, but would fail for the Kurento case.

I think that a more robust fix would be to make sure that the randomly generated ID is communicated to the javascript layer properly from Swift. I looked at doing this myself, but my Swift-fu is weak, and I couldn't figure out how to communicate the id properly in a short period of time.

[ibc]

@justindujardin I don't understand. #164 was already fixed so long ago, and random stream ID generated in Swift land is properly exposed/propagated to JavaScript 1, 2.

[justindujardin]

@ibc I setup a test to show the problem happening in the debugger. The issue, I now recall, is that when the removestream event is generated, it does not have the correct id.

During the stream add, the id is setup properly:

During removestream, the UUID is not present in the streamId:

[ibc]

The bug is here:

When the pc.onaddstream fires, the Swift code creates a PluginMediaStream wrapper that has a id property defined as follows:

self.id = rtcMediaStream.label + "-" + UUID().uuidString

Such a id value is propagated to JS becoming the stream.id property.

However, when the onremovestream fires, the swift codes does not internally get its corresponding Swift PluginMediaStream but just fires an event to the JS by just reporting the rtcMediaStream.label (being rtcMediaStream the ObjC RTCMediaStream instance), as you can see here:

self.eventListener([
    "type": "removestream",
    "streamId": rtcMediaStream.label
])

Obviously, rtcMediaStream.label does not match rtcMediaStream.label + "-" + UUID().uuidString, so here the problem.

This bug is a regression produced by #164, which indeed solves a different issue, but creates this one.

iosrtcPlugin.swift stores the PluginMediaStream.swift instances in a map indexed by their id above, so when a remote stream is removed and the PluginRTCPeerConnection.swift invokes this code it does not even remove the stream from the internal map. So the issue happens in both JS and Swift lands.

Since the ObjC RTCMediaStream.h does not have a seteable id property, the plugin can not set the created id into it. So the solution coming to my mind is the following:

• PluginRTCPeerConnection.swift should hold a map with:
  
  
  
  • Key: The ObjC RTCMediaStream instance.
  
  
  • Value: The id as created here.
  
  
• When onremovestream is fired within PluginRTCPeerConnection.swift, it should retrieve its corresponding id from the previous map and propagate it to the JS (via the removestream event) rather than the rtcMediaStream.label.

Said that:

• I don't know if Swift allows having a "map" with class instances as keys, but for sure a similar approach can be achieved.
• I don't have a iOS device so I cannot do this.
• I hope the info given here can help others to create a PR that fixes the issue.

[mariuszbeltowski]

Did any of you guys manage to fix it? @magestican @ibc @saghul @justindujardin

[l7s]

Hi, sorry can't do PR (as got only internal git repos behind firewall), but here is patch which fixes the issue for us:

```
--- a/src/PluginRTCPeerConnection.swift
+++ b/src/cordova-plugin-iosrtc/PluginRTCPeerConnection.swift
@@ -19,6 +19,7 @@ class PluginRTCPeerConnection : NSObject, RTCPeerConnectionDelegate, RTCSessionD
var onSetDescriptionSuccessCallback: (() -> Void)!
var onSetDescriptionFailureCallback: ((_ error: Error) -> Void)!
var onGetStatsCallback: ((_ array: NSArray) -> Void)!

• var mediaStreamIdMap: [String: String]

init(
    rtcPeerConnectionFactory: RTCPeerConnectionFactory,

@@ -36,6 +37,7 @@ class PluginRTCPeerConnection : NSObject, RTCPeerConnectionDelegate, RTCSessionD
self.eventListener = eventListener
self.eventListenerForAddStream = eventListenerForAddStream
self.eventListenerForRemoveStream = eventListenerForRemoveStream

• self.mediaStreamIdMap = [:]
  }

@@ -544,10 +546,13 @@ class PluginRTCPeerConnection : NSObject, RTCPeerConnectionDelegate, RTCSessionD

func peerConnection(_ rtcPeerConnection: RTCPeerConnection!,
    addedStream rtcMediaStream: RTCMediaStream!) {

- NSLog("PluginRTCPeerConnection | onaddstream")
-
+
let pluginMediaStream = PluginMediaStream(rtcMediaStream: rtcMediaStream)

• NSLog("PluginRTCPeerConnection | onaddstream [" + pluginMediaStream.id + "]")
• 
  
  
  
  • self.mediaStreamIdMap[rtcMediaStream.label] = pluginMediaStream.id
  
  

• pluginMediaStream.run()
  
  // Let the plugin store it in its dictionary.
  

  @@ -563,14 +568,19 @@ class PluginRTCPeerConnection : NSObject, RTCPeerConnectionDelegate, RTCSessionD

  func peerConnection(_ rtcPeerConnection: RTCPeerConnection!,
  removedStream rtcMediaStream: RTCMediaStream!) {

• NSLog("PluginRTCPeerConnection | onremovestream")
• 
  
  
  
  • let streamId = self.mediaStreamIdMap[rtcMediaStream.label]!
  
  
• 
  
  
  
  • self.mediaStreamIdMap.removeValue(forKey: rtcMediaStream.label)
  
  

• • NSLog("PluginRTCPeerConnection | onremovestream [" + streamId + "]")

    // Let the plugin remove it from its dictionary.
    self.eventListenerForRemoveStream(rtcMediaStream.label)

    self.eventListener([
    "type": "removestream",

• "streamId": rtcMediaStream.label // NOTE: No "id" property yet.
• "streamId": streamId
  ])
  }
  ```

Regards,
Chris

[hthetiot]

Will make PR @l7s thx.

[hthetiot]

Will also investigate this comment

• https://github.com/cordova-rtc/cordova-plugin-iosrtc/issues/164#issuecomment-315798369

[hthetiot]

@l7s Thank you I made a PR and confirmed the fix, will be on 5.0.2

• https://github.com/cordova-rtc/cordova-plugin-iosrtc/pull/383