[webkit-dev] WebKit caching

Darin Adler darin at apple.com
Sat Apr 11 23:51:43 PDT 2009

On Apr 11, 2009, at 6:54 PM, Adam Thorsen wrote:

> I also noticed recently that there is a "Disable Caches" option  
> under the Develop menu on Safari.  I tested it using the same  
> procedure and it indeed did not cache the javascript, so I know this  
> is possible one way or another.

It’s true, Disable Caches does this.

In fact, I read over the implementation of that menu item before  
answering your original question. All that Safari does when that menu  
item is selected is:

     [[WebPreferences standardPreferences]  
     [[NSURLCache sharedURLCache] setDiskCapacity:0];

I’m not sure why that works better in Safari than in your test  

>         NSURL * url = [aRequest URL];
>         NSURLRequest * cachelessRequest = [NSURLRequest  
> requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData  
> timeoutInterval:100];
>         return cachelessRequest;

This code in your willSendRequest delegate method may be causing a  
problem. It discards the request and creates a new one, taking only  
the URL from the original request. That’s a problem because there are  
other important fields in the request, such as the HTTP method, HTTP  
body, and HTTP header fields. If you want to change the cache policy  
(and you should not need to do this, see my original message), you  
would need code more like this:

     if ([request cachePolicy] == NSURLRequestReloadIgnoringCacheData)
         return request;

     NSURLRequest *cachelessRequest = [aRequest mutableCopy];
     return cachelessRequest;

Hope that helps.

     -- Darin

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