Jimmy Jarvis created CB-1318:
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Summary: Callback Logic Not Implemented Correctly - Native
Asynchronous Completion Can Call Wrong Logic in Javascript - Requires
Non-recurring Unique ID as Suggested
Key: CB-1318
URL: https://issues.apache.org/jira/browse/CB-1318
Project: Apache Cordova
Issue Type: Bug
Components: iOS
Affects Versions: 2.0.0
Reporter: Jimmy Jarvis
Assignee: Shazron Abdullah
Priority: Critical
This bug creates very difficult to find execution anomalies for any
asynchronous callback that occurs when the calling context has changed.
PROBLEM: Cordova callback logic can trigger the callback function of an
unrelated call from a different context. When a call from Javascript is made,
Cordova generates a new callbackId, adds it to the cordova.callbacks array, and
passes it along to the native code. Some time later, when the native code
completes the request, it injects javascript to call the callbackSuccess or
callbackError function. The respective callback handler looks up the callback
attributes from the cordova.callbacks array and executes the original caller's
completion function. The problem is each page, or reload of a page, resets the
callbackId counter to zero and new calls end up reusing the same callbackId,
even though the native code haS not yet completed the prior request. This can
occur upon a new page load or reload upon an empty href in an anchor tag. A
call to native code from page1.html could trigger the completion routine on
page2.html because the native code has no context of the change on the other
side of the bridge.
SOLUTION: Replace the incrementing callbackId with a unique identifier to
insure only the caller's completion logic will be called. I have done this with
a Pseudo-GUID generator. Fix outlined below:
// REPLACE THIS LINE in both cordova.2.0.0.js and cordova.ios.js
callbackId = service + cordova.callbackId++; // BUG: incrementing
Id's can call unrelated callback logic
// WITH THIS LINE
callbackId = service + ":" +
'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {var r =
Math.random()*16|0,v=c=='x'?r:r&0x3|0x8;return v.toString(16);}); // Generate
unique callbackID with Pseudo-GUID
This fix insures no code will execute if the caller's context has changed and
is a more well formatted callbackId.
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