iOS 清除web cookies

NSHTTPCookie *cookie;
    NSHTTPCookieStorage *storage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
    for (cookie in [storage cookies])
    {
        [storage deleteCookie:cookie];
    }
    //缓存web清除
    [[NSURLCache sharedURLCache] removeAllCachedResponses];

    [self.webView loadRequest:[NSURLRequest requestWithURL:url]];

    if (url) {//清除所有cookie
        NSArray *cookies = [[NSHTTPCookieStorage sharedHTTPCookieStorage] cookiesForURL:url];
        for (int i = ; i < [cookies count]; i++) {
            NSHTTPCookie *cookie = (NSHTTPCookie *)[cookies objectAtIndex:i];
            [[NSHTTPCookieStorage sharedHTTPCookieStorage] deleteCookie:cookie];

        }
    }
    //清除某一特定的cookie方法
    NSArray * cookArray = [[NSHTTPCookieStorage sharedHTTPCookieStorage] cookiesForURL:url];
    for (NSHTTPCookie*cookie in cookArray) {
        if ([cookie.name isEqualToString:@"cookiename"]) {
            [[NSHTTPCookieStorage sharedHTTPCookieStorage] deleteCookie:cookie];
        }
    }