清除UIWebView的缓存

    //清除UIWebView的缓存

    [ [NSURLCache  sharedURLCache ]removeAllCachedResponses];

附：NSUrlcache的公有方法

- (void)removeCachedResponseForRequest:(NSURLRequest *)request;

- (void)removeAllCachedResponses;

获取当前缓存大小：

/*! 

    @method currentMemoryUsage

    @abstract Returns the current amount of space consumed by the

    in-memory cache of the receiver.

    @discussion This size, measured in bytes, indicates the current

    usage of the in-memory cache. 

    @result the current usage of the in-memory cache of the receiver.

*/

- (NSUInteger)currentMemoryUsage;

/*! 

    @method currentDiskUsage

    @abstract Returns the current amount of space consumed by the

    on-disk cache of the receiver.

    @discussion This size, measured in bytes, indicates the current

    usage of the on-disk cache. 

    @result the current usage of the on-disk cache of the receiver.

*/

- (NSUInteger)currentDiskUsage;