     class func loadUserAccount() -> UserAccount? {
         
         if UserAccount.account != nil {
-            return UserAccount.account
+            return nil
         }
         
         guard let account = NSKeyedUnarchiver.unarchiveObjectWithFile(UserAccount.filePath) as? UserAccount else {
             return UserAccount.account
         }
+        
+        // 校验是否过期了
+        /*
+        guard let date = account.expires_Date else {
+            return nil
+        }
+        if date.compare(NSDate()) == NSComparisonResult.OrderedAscending {
+            return nil
+        }
+        */
+        SXMLog(account.expires_Date)
+        SXMLog(NSDate())
+        guard let date = account.expires_Date where date.compare(NSDate()) == NSComparisonResult.OrderedAscending else {
+            SXMLog("过期了")
+            return nil
+        }
+        
         UserAccount.account = account
         
         return UserAccount.account

        aCoder.encodeObject(access_token, forKey: "access_token")
        aCoder.encodeInteger(expires_in, forKey: "expires_in")
        aCoder.encodeObject(uid, forKey: "uid")
    }
    
    required init?(coder aDecoder: NSCoder) {
        self.access_token = aDecoder.decodeObjectForKey("access_token") as? String
        self.expires_in = aDecoder.decodeIntegerForKey("expires_in") as Int
        self.uid = aDecoder.decodeObjectForKey("uid") as? String
    }

}

class UserAccount: NSObject, NSCoding {

    var access_token: String?
    // 从授权开始 多少秒之后过期时间
    var expires_in: Int = 0 {
        didSet {
            expires_Date = NSDate(timeIntervalSinceNow: NSTimeInterval(expires_in))
        }
    }
    // 真正过期时间
    var expires_Date: NSDate?
    var uid: String?
    
    init(dict: [String: AnyObject]) {
