[TIMOB-786] crash using 'this' in removeEventListener

GitHub Issue	n/a
Type	Bug
Priority	Medium
Status	Closed
Resolution	Invalid
Resolution Date	2011-04-15T02:36:25.000+0000
Affected Version/s	n/a
Fix Version/s	Release 1.4.0
Components	iOS
Labels	n/a
Reporter	Nolan Wright
Assignee	Jeff Haynie
Created	2011-04-15T02:36:22.000+0000
Updated	2017-03-02T18:40:41.000+0000

Description

add this code to app.js

Ti.App.addEventListener('hello', function(){

Ti.API.info('Hello event fired!');
Ti.App.removeEventListener('hello', this);

});

Ti.App.fireEvent('hello');

Comments

Stephen Tramer 2011-04-15

Worse than expected. The 'this' symbol does not play nice in a lot of situations.
Stephen Tramer 2011-04-15

Okay, see http://www.quirksmode.org/js/this.html">http://www.quirksmode.org/js/this.html. Apparently 'this' is supposed to screw up if you don't use it when a function is bound to an object, but we should still consider it a (low-priority) issue.
Justin 2011-04-15

I have windows with events that I would like to fire only once. I'm using the code pattern above to remove the event promptly, but it crashes at removeEventListener. Know of a workaround?
Stephen Tramer 2011-04-15
I think this will do what you want (let me know if it doesn't):
```
   a.addEventListener('action', function(e) {
      // Do stuff
      Ti.App.removeEventListener('action', e.source);
   }
   
```
This will probably have to be the pattern you use in the future as well. 'this' support in event listeners was erroneous in 0.8 because an event listener isn't REALLY a function attached to an object (see the link in the above comments for more).
Justin 2011-04-15

That works. Thanks Stephen!
Justin 2011-04-15

Whoops, I take that back. It doesn't seem to work.
Stephen Tramer 2011-04-15

Can you give me any additional information about the failure, or is it just that the event listener isn't removed? I can create a bug for this if there isn't one already.
Justin 2011-04-15

The event listener appeared not to be removed.
Stephen Tramer 2011-04-15

Thanks for the information. I've created #1043 and will address the issue as quickly as I can.
Justin 2011-04-15

Thanks Stephen
Stephen Tramer 2011-04-15

Justin, I updated #1043 with some sample code that shows how to appropriately remove an event listener. Please let me know if it doesn't work for you in that ticket, and re-open it if necessary.
Justin 2011-04-15

Currently using that, thanks Stephen.
Stephen Tramer 2011-04-15

See #1043. Also, functions in event listeners do not belong to an object; they're callbacks. Marking this invalid.
Lee Morris 2017-03-02

Closing as invalid.

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