SharedObject.flush() the silent killer.

We launched our Video Chat Application to mostly good reviews from the user community.  One of our biggest complaints/bugs was “The app doesn’t load… it just displays a blank white page after the “loading” screen goes away”.  We’d tried old Flash player versions, older browsers, multiple OS’s and STILL couldn’t reliably duplicate the error.  After a couple weeks of the app being live someone started a thread on the community forums titled “Think I know why people are having problems getting into chat..”.  Sure enough the user pointed out a development over sight.  It seems that if a user has set their “Local Storage” settings in Flash to 0 the app would fail to load, the forum thread gave a quick description on how to set this to a higher number.

We weren’t exactly sure as to why this happened on some systems nor why your average user would have changed this (testing locally wouldn’t duplicate the bug, but the fix was indeed working for people left and right).  So we let people in customer service know about this fix… but that still didn’t answer why it was breaking.  We knew it had to do with local storage (obviously) and more than likely it was related to saving Local Shared Objects to the clients system to keep their settings preferences between app sessions.  What I found out just really pissed me off more than anything.

So turns out if you’re using Local Shared Objects and a user has disabled local storage your app will run fine.   You can freely write and read to the Shared Object without any issues the problem arose when you’d issues a SharedObject.flush().  But that wouldn’t fail UNLESS a user has checked “never ask again”.  See if a user had set the number to 0 when you issued a flush() the app would ask them for permission but if they had checked “never ask again” the SharedObject would throw a fatal error (that doesn’t even register in the Debug Flash Player mind you).

In short… if using Local Shared Objects in your app your code should look something like this.

public var my_so:SharedObject = SharedObject.getLocal('your_so');public function save_so():Boolean{    var so_status:String;    try    {        so_status = my_so.flush();    }    catch(e)    {        Alert.show("you'll need to enable local storage to save settings.");        return false;    }    if(so_status == "pending")    {        // set to 0 ... prompted user for allow or deny... might have saved it.        return false;    }    else if(so_status == "flushed")    {        // successfully wrote SO to disk.    }    return true;}