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Re: WebView resource loading
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Re: WebView resource loading

Rob Keniger wrote: 

On Aug 23, 2007, at 10:40 AM, Rudi Sherry wrote:

You can create a new NSURLProtocol; this is pretty low-level and should be asked if it can handle any request. You're given some sort of Protocol client to which you hand the bytes, and you are told when to start and stop. 


There is a great sample project from Apple which shows how to do this:

http://developer.apple.com/samplecode/SpecialPictureProtocol/


The OP didn't say why he wants to control the resource loading, but I will add a cautionary note here just in case he's doing something tricky.

If you are doing this so that you can return different data at different times for the same resource URL in the page, then you have a problem. (For example, your page contains the element <img href="MyImage.gif" /> and when you see the "MyImage.gif" URL you look at some data and decide what picture you should really display, and it can be a different picture every time.) The problem is not in the currently shipping WebKit, but it is in the nightly builds and, I assume, will be in the WebKit that supports Safari 3 and ships with Leopard. What happens is that when page resources are loaded, their data is cached, and the cached data is keyed by the original URL. This means that whatever data you return the first time you intercept that URL will be used subsequently. Your webView:resource:willSendRequest:redirectResponse:fromDataSource: delegate will only be called the first time, and the data will be read from cache after that.

I ran across this when my resources were all file:/// URLs, and it also occurred when I switched everything to use my own custom protocol. My protocol loader only got called the first time, but not subsequently for the same original resource URL. It also did not seem to matter that I specified no caching in my NSURLResponse that I used to return the data. It was cached anyway.

If this doesn't affect you, I would still suggest that you download the WebKit sources, build the framework, and test your app against it. Things have been tightened up in this area. I assume this was done to address security holes. The result is a difference in behavior between the current and newer WebKit versions.

- Rush
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References: 


 >WebView resource loading (From: Mike Gargano <email@hidden>)


 >Re: WebView resource loading (From: Rudi Sherry <email@hidden>)


 >Re: WebView resource loading (From: Rob Keniger <email@hidden>)























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