清除UIWebView缓存

//清除cookies
NSHTTPCookie *cookie;
NSHTTPCookieStorage *storage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
for (cookie in [storage cookies]) 
{
    [storage deleteCookie:cookie];
}
//退出登录实现

//清除UIWebView的缓存
[[NSURLCachesharedURLCache] removeAllCachedResponses];

NSURLCache * cache = [NSURLCache sharedURLCache];  

 [cache removeAllCachedResponses];  

[cache setDiskCapacity:0];  

[cache setMemoryCapacity:0];