Is Safari on iOS 6 caching $.ajax results?

Question

Since the upgrade to iOS 6, we are seeing Safari's web view take the liberty of caching $.ajax calls. This is in the context of a PhoneGap application so it is using the Safari WebView. Our $.ajax calls are POST methods and we have cache set to false {cache:false}, but still this is happening. We tried manually adding a TimeStamp to the headers but it did not help.

We did more research and found that Safari is only returning cached results for web services that have a function signature that is static and does not change from call to call. For instance, imagine a function called something like:

getNewRecordID(intRecordType)

This function receives the same input parameters over and over again, but the data it returns should be different every time.

Must be in Apple's haste to make iOS 6 zip along impressively they got too happy with the cache settings. Has anyone else seen this behavior on iOS 6? If so, what exactly is causing it?

---

The workaround that we found was to modify the function signature to be something like this:

getNewRecordID(intRecordType, strTimestamp)

and then always pass in a TimeStamp parameter as well, and just discard that value on the server side. This works around the issue. I hope this helps some other poor soul who spends 15 hours on this issue like I did!

Answer 1

Depending on the app you can trouble shoot the issue now in iOS 6 using Safari>Advanced>Web Inspector so that is helpful with this situation.

Connect the phone to Safari on a Mac an then use the developer menu to trouble shoot the web app.

Clear the website data on the iPhone after update to iOS6, including specific to the app using a Web View. Only one app had an issue and this solved it during IOS6 Beta testing way back, since then no real problems.

You may need to look at your app as well, check out NSURLCache if in a WebView in a custom app.

https://developer.apple.com/library/ios/#documentation/Cocoa/Reference/Foundation/Classes/NSURLCache_Class/Reference/Reference.html#//apple_ref/doc/uid/TP40003754

I guess depending on the true nature of your problem, implementation, etc. ..

Ref: $.ajax calls

Answer 2

I had the same problem with a webapp getting data from ASP.NET webservice

This worked for me:

public WebService()
{
    HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
    ...
}

Answer 3

I suggest a workaround to modify the function signature to be something like this:

getNewRecordID(intRecordType, strTimestamp) and then always pass in a TimeStamp parameter as well, and just discard that value on the server side. This works around the issue.

Answer 4

I hope this can be of use to other developers banging their head against the wall on this one. I found that any of the following prevents Safari on iOS 6 from caching the POST response:

• adding [cache-control: no-cache] in the request headers
• adding a variable URL parameter such as the current time
• adding [pragma: no-cache] in the response headers
• adding [cache-control: no-cache] in the response headers

My solution was the following in my Javascript (all my AJAX requests are POST).

$.ajaxSetup({
    type: 'POST',
    headers: { "cache-control": "no-cache" }
});

I also add the [pragma: no-cache] header to many of my server responses.

If you use the above solution be aware that any $.ajax() calls you make that are set to global: false will NOT use the settings specified in $.ajaxSetup(), so you will need to add the headers in again.

Answer 5

It worked with ASP.NET only after adding the pragma:no-cache header in IIS. Cache-Control: no-cache was not enough.

Answer 6

Finally, I've a solution to my uploading problem.

In JavaScript:

var xhr = new XMLHttpRequest();
xhr.open("post", 'uploader.php', true);
xhr.setRequestHeader("pragma", "no-cache");

In PHP:

header('cache-control: no-cache');