ios - 如何快速编写 dynamodb 查询以获取具有特定分区键的所有值

Question

我无法找到一种方法来快速编写 dynamodb 查询来获取具有特定分区键的结果。

例如，假设我的分区键是“bigCompany”，排序键是“email”。现在我想获取所有名称为“bigCompany”的电子邮件为“xyz”。

作为引用，我的代码结构与下面的加载函数非常相似。但是这个使用 .load 来获取一个值而不是查询。基本上我需要找到一种方法来调用 dynamoDBOBjectMapper .query() 鉴于我上面提到的约束。任何帮助将不胜感激!

func getTableRow() {
    let dynamoDBObjectMapper = AWSDynamoDBObjectMapper.defaultDynamoDBObjectMapper()

    //tableRow?.UserId --> (tableRow?.UserId)!
    dynamoDBObjectMapper .load(DDBTableRow.self, hashKey: (tableRow?.UserId)!, rangeKey: tableRow?.GameTitle) .continueWithExecutor(AWSExecutor.mainThreadExecutor(), withBlock: { (task:AWSTask!) -> AnyObject! in
        if (task.error == nil) {
            if (task.result != nil) {
                let tableRow = task.result as! DDBTableRow
                self.hashKeyTextField.text = tableRow.UserId
                self.rangeKeyTextField.text = tableRow.GameTitle
                self.attribute1TextField.text = tableRow.TopScore?.stringValue
                self.attribute2TextField.text = tableRow.Wins?.stringValue
                self.attribute3TextField.text = tableRow.Losses?.stringValue
            }
        } else {
            print("Error: \(task.error)")
            let alertController = UIAlertController(title: "Failed to get item from table.", message: task.error!.description, preferredStyle: UIAlertControllerStyle.Alert)
            let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Cancel, handler: { (action:UIAlertAction) -> Void in
            })
            alertController.addAction(okAction)
            self.presentViewController(alertController, animated: true, completion: nil)

        }
        return nil
    })
}

Answer 1

想通了。他们的关键是正确使用 keyConditionExpression。以下是我的回答。

            let queryExpression = AWSDynamoDBQueryExpression()

            queryExpression.keyConditionExpression = "#bigCompany = :bigCompany"
            queryExpression.expressionAttributeNames = ["#bigCompany": "bigCompany",]
            queryExpression.expressionAttributeValues = [":bigCompany" : self.bigCompany,]

            dynamoDBObjectMapper.query(Requests.self, expression: queryExpression) .continue(with: AWSExecutor.immediate(), with: { (task:AWSTask!) -> AnyObject! in
                //If added successfully
                if((task.result) != nil) {
                    let results = task.result! as AWSDynamoDBPaginatedOutput
                    print(results.items)
                } 
                else {
                    //do error checking here
                }
            })