Using getTimer() as a Cache Killer

[Kwangle]

Hi All,

I have recently been working on a Flash file that dynamically loads a movie based on the contents of a simple XML file. I was concerned about caching issues so tried to set up the code to avoid the XML file being cached causing the wrong content to be loaded. I did this by adding a dummy query string to the file link which is a numerical value generated by getTimer().

In practice the system mostly worked but occasionally old content would load even though the XML had been changed. The code runs a setInterval that checks the XML every 20 seconds and checks if the loaded file specfied has changed. The code loads the XML with the following code:

holderXML.load("http://www.mysite/myscripts/myxml.xml?cachekill="+getTimer());

The getTimer() functions starts counting in milliseconds as soon as the movie runs so there is a chance that the same query string is assigned to more than one file, meaning that an old cached version is loaded instead of the new, live file. I am now thinking about ways to improve this code and generate unique values for the query string. I thought using the epoch time - the time in milliseconds from which Flash calculates time and dates which is set to Jan 01 1970 - would generate a new value every millisecond and maybe adding an additional random number to that value to further reduce the chance of the same query string being generated more than once.

this.onEnterFrame = function () {

var nowDate:Date = new Date();

nowTime = nowDate.getTime();

randomNum = Math.round(Math.random()*10000);

holderXML.load("http://www.mysite/myscripts/myxml.xml?cachekill="+nowTime+"rnd"+randomNum);

}

Is there a better way of avoiding cache issues in Flash? Any comments and advice would be appreciated.

[Ned Murphy]

Using anything that won't be the same value twice is sufficient.  Using Date.getTime() should work by itself.  Using Math.random() by itself is usually sufficient as well.