iOS: No way to handle app termination on JS side

I’m trying to do some clean up on JS side (mainly - send a single HTTP request) when app is closed by user. As some answers on SO suggest, I tried to implement applicationWillTerminate method in AppDelegate.m and pass a prop to rootView:

- (void)applicationWillTerminate:(UIApplication *)application
{
  NSMutableDictionary *newProps = [NSMutableDictionary dictionary];
  if (self.rootView.appProperties != nil) {
    [newProps addEntriesFromDictionary:self.rootView.appProperties];
  }
  newProps[@"appWillTerminate"] = @YES;
  self.rootView.appProperties = newProps;
}

and then in my Root view on JS side:

componentWillReceiveProps(nextProps) {
    if (nextProps.appWillTerminate) {
        // Do clean up
    }
}

but JS code inside if clause is not executed.

So I was wondering if there is any other way to do something on JS side when app terminates. I was also looking into AppState component, but it also doesn’t support app termination.

[aleclarson]

Could a Facebook employee that knows more about the native bridge help us?

It would be ideal to handle applicationWillTerminate and background tasks from the JS side.

Edit: It looks like asynchronous code will never complete from within applicationWillTerminate , which means the native bridge cannot work.

Right now, the best you can do is synchronously write your data on the native side. Then, when the application is opened later, read the data and pass it to the JS side. Of course, this means you cannot do any cleanup on the JS side before the application is terminated. You’ll need to send the wanted data from JS to native before applicationWillTerminate is called.

Seems like Apple will have to “fix” this. When/if the native bridge becomes synchronous, you could at least shoot off an HTTPS request (from the JS side) before the application terminates. But asynchronous code would still be off limits.

[jcharlet]

hi @aleclarson , do you have some code to share to show how to write data on native side to handle app termination as you explained…? I’m using asyncStorage at the moment to store data, and I have no idea how to access/store stuff on native side. Any hint/ things you would recommend looking at?