Is it possible to prevent an NSURLRequest from caching data or remove cached data following a request?

Question

Hiya,

On iPhone, I perform a HTTP request using NSURLRequest for a chunk of data. Object allocation spikes and I assign the data accordingly. When I finish with the data, I free it up accordingly - however instruments doesn't show any data to have been freed!

My theory is that by default HTTP requests are cached, however - I don't want my iPhone app to cache this data.

Is there a way to clear this cache after a request or prevent any data from being cached in the first place?

I've tried using all the cache policies documented a little like below:

NSMutableURLRequest *theRequest = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:url]];
theRequest.cachePolicy = NSURLRequestReloadIgnoringLocalCacheData;

but nothing seems to free up the memory!

Any help here would be much appreciated.

Thanks! Nick.

Answer 1

If you use NSURLConnection take a look at the delegate:

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse

Return Value

The actual cached response to store in the cache. The delegate may return cachedResponse unmodified, return a modified cached response, or return nil if no cached response should be stored for the connection.

Answer 2

Usually it's easier to create the request like this

NSURLRequest *request = [NSURLRequest requestWithURL:url
      cachePolicy:NSURLRequestReloadIgnoringCacheData
      timeoutInterval:60.0];

Then create the connection

NSURLConnection *conn = [NSURLConnection connectionWithRequest:request
       delegate:self];

and implement the connection:willCacheResponse: method on the delegate. Just returning nil should do it.

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse {
  return nil;
}

Answer 3

I have the same problem in my app when I requested info from twitter. In my case I didn't need to preserve those credentials, so I simple erase them using the next code:

- (void) eraseCredentials{
NSURLCredentialStorage *credentialsStorage = [NSURLCredentialStorage sharedCredentialStorage];
NSDictionary *allCredentials = [credentialsStorage allCredentials];

//iterate through all credentials to find the twitter host
for (NSURLProtectionSpace *protectionSpace in allCredentials)
 if ([[protectionSpace host] isEqualToString:@"twitter.com"]){
        //to get the twitter's credentials
  NSDictionary *credentials = [credentialsStorage credentialsForProtectionSpace:protectionSpace];
        //iterate through twitter's credentials, and erase them all
  for (NSString *credentialKey in credentials)
   [credentialsStorage removeCredential:[credentials objectForKey:credentialKey] forProtectionSpace:protectionSpace];
 }
}

I hope it works for somebody :)

Answer 4

So does calling a url this way cache the response on the iPhone ? I understand the need to remove the cache from memory but does it save the data from the request in some other location?

[myWebView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://SomeSiteName.com/mobile/iphonelogin.aspx"]]];

Answer 5

• (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse

  how i use this ..where i use it please give detail description ...i am new to iphone..

  what is the purpose of this function..