iOS清除UIWebView缓存

使用iOS的webview会自动进行缓存，在开发的时候要记得清除Cookie和缓存。

/**清除缓存和cookie*/  
- (void)cleanCacheAndCookie{  
//清除cookies  
NSHTTPCookie *cookie;  
NSHTTPCookieStorage *storage = [NSHTTPCookieStorage sharedHTTPCookieStorage];  
for (cookie in [storage cookies]){  
    [storage deleteCookie:cookie];  
}  
//清除UIWebView的缓存  
[[NSURLCache sharedURLCache] removeAllCachedResponses];  
NSURLCache * cache = [NSURLCache sharedURLCache];  
[cache removeAllCachedResponses];  
[cache setDiskCapacity:0];  
[cache setMemoryCapacity:0];  
}