Question

首先，我想用DynamoDB实现的目标：

- ＆GT; （我试图在登录系统的扫描过滤器中包含用户名和密码。因此，如果对于电子邮件/用户和密码组合，scan AWSDynamoDBObjectMapper方法返回一个对象，则登录成功，否则不。）

出了什么问题？

我一直在努力阅读Github上的文档和示例代码，但似乎都没有正确使用它的示例。从文档中我只发现scanFilter是NSDictionary类型。所以我尝试包含多个参数用于过滤（UserName/UserEmail and Password），并且无法扫描结果。

 scanExpression.scanFilter = @{@"Password": passwordCondition, UserNameOrUserEmail : usernameOrEmailCondition};

但是，如果我只传递一个参数，它会工作并返回一个对象，或者说一行数据库。

scanExpression.scanFilter = @{@"Password": passwordCondition};

完整的参考代码（类似的Android代码可以正常工作，当我提到同事的时候，谁在做Android。）

// Check if email or username and decide DynamoDB Attribute accordingly.
NSString *UserNameOrUserEmail;   
if ([usernameOrEmail rangeOfString:@"@"].location == NSNotFound) 
    UserNameOrUserEmail = @"UserName";
else
    UserNameOrUserEmail = @"UserEmail";

AWSDynamoDBScanExpression *scanExpression = [AWSDynamoDBScanExpression new];

AWSDynamoDBCondition *passwordCondition = [AWSDynamoDBCondition new];
AWSDynamoDBAttributeValue *passwordAttribute = [AWSDynamoDBAttributeValue new];
passwordAttribute.S = password;
passwordCondition.attributeValueList = @[passwordAttribute];
passwordCondition.comparisonOperator = AWSDynamoDBComparisonOperatorEQ;

AWSDynamoDBCondition *usernameOrEmailCondition = [AWSDynamoDBCondition new];
AWSDynamoDBAttributeValue *usernameOrEmailAttribute = [AWSDynamoDBAttributeValue new];
usernameOrEmailAttribute.S = @"sammy@hhd.com";//usernameOrEmail;
usernameOrEmailCondition.attributeValueList = @[usernameOrEmailAttribute];
usernameOrEmailCondition.comparisonOperator = AWSDynamoDBComparisonOperatorEQ;

//Apply filter condtions: http://stackoverflow.com/a/27856299/818506
scanExpression.scanFilter = @{@"Password": passwordCondition, UserNameOrUserEmail : usernameOrEmailCondition}; //@{@"UserEmail": usernameOrEmailCondition};//

 //^^^^^^^^^^^^^^^^^^^^^^^^^^^Is this correct?^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^    

//Perform a scan:
[[dynamoDBObjectMapper scan:[User class] expression:scanExpression]continueWithBlock: ^id (AWSTask *task){

    if (task.error) {
        NSLog(@"The request failed. Error: [%@]", task.error);
    }
    if (task.exception) {
        NSLog(@"The request failed. Exception: [%@]", task.exception);
    }
    if (task.result) {
        AWSDynamoDBPaginatedOutput *paginatedOutput = task.result;
        for (User *user in paginatedOutput.items) {
            isLoginSuccessful = YES;
         }
        completionHandler(isLoginSuccessful);
    }
    return nil;
}];

任何建议/想法/评论都会受到赞赏。

谢谢，罗汉。

Answer 1

我在处理类似问题的时候发现了这个帖子。以下是我解决它的方法：

    let objectMapper = AWSDynamoDBObjectMapper.default()
    let scanExpression = AWSDynamoDBScanExpression()

    scanExpression.filterExpression = "#UserNameOrUserEmail = :UserNameOrUserEmail AND #password = :follows"
    scanExpression.expressionAttributeNames = ["#UserNameOrUserEmail": "UserNameOrUserEmail" , "#password": "password" ,]
    scanExpression.expressionAttributeValues = [":UserNameOrUserEmail": "sammy@hhd.com", ":password": password ,]

    objectMapper.scan(User.self, expression: scanExpression) { (response: AWSDynamoDBPaginatedOutput?, error: Error?) in
        // handle data or error here...
    }

只是它可以帮助别人。

DynamoDB iOS：AWSDynamoDBScanExpression为scanFilter属性提供多个参数

1 个答案: