iOS关于Cookie验证登录状态

1、第一次进入应用，登录获取Cookie，此时如果用到的是AFN去获取接口数据，Cookie已经写入了，所以无需处理，每次请求的时候，会自动将该cookie传给后台去验证

2、将Cookie缓存到本地：

NSData *cookiesData = [NSKeyedArchiver archivedDataWithRootObject: [[NSHTTPCookieStorage sharedHTTPCookieStorage] cookies]];
                NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
                [defaults setObject: cookiesData forKey:@"Cookie"];
                [defaults synchronize];

3、当第二次进入应用的时候，先判断NSUserDefault是否有缓存的Cookie，如果有，需要将cookie写入，然后进入应用

NSArray *cookies = [NSKeyedUnarchiver unarchiveObjectWithData:[[NSUserDefaults standardUserDefaults] objectForKey:@"Cookie"]];
                NSHTTPCookieStorage * cookieStorage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
                for (NSHTTPCookie * cookie in cookies){
                    [cookieStorage setCookie: cookie];
                }

4、当用户选择退出登录，需要清除缓存中的cookie，同时要将NSUserDefault中的Cookie删除

（1）清除请求头中的Cookie：

NSHTTPCookieStorage *manager = [NSHTTPCookieStorage sharedHTTPCookieStorage];
                NSArray *cookieStorage = [[NSHTTPCookieStorage sharedHTTPCookieStorage] cookies];
                for (NSHTTPCookie *cookie in cookieStorage) {
                    [manager deleteCookie:cookie];
                }

（2）清除NSUserDefault中的Cookie

[[NSUserDefaults standardUserDefaults] removeObjectForKey:@"Cookie"];

[defaults synchronize];