Amazon web services 使用Swift进行Amazon AWS DynamoDB查询的最佳方法?
我最近为我的iOS应用程序实现了AWS SDK,我正在Swift中开发。我已经连接到我的DB实例,并且能够获得查询响应,但是,我正在努力将其转换为可用数据。我对Swift、AWS和编程都比较陌生,所以可能遗漏了一些明显的东西 我的代码如下:Amazon web services 使用Swift进行Amazon AWS DynamoDB查询的最佳方法?,amazon-web-services,swift,amazon-dynamodb,Amazon Web Services,Swift,Amazon Dynamodb,我最近为我的iOS应用程序实现了AWS SDK,我正在Swift中开发。我已经连接到我的DB实例,并且能够获得查询响应,但是,我正在努力将其转换为可用数据。我对Swift、AWS和编程都比较陌生,所以可能遗漏了一些明显的东西 我的代码如下: let atVal = AWSDynamoDBAttributeValue() atVal.S = "123456abc" let condition = AWSDynamoDBCondition() condition.co
let atVal = AWSDynamoDBAttributeValue()
atVal.S = "123456abc"
let condition = AWSDynamoDBCondition()
condition.comparisonOperator = AWSDynamoDBComparisonOperator.EQ
condition.attributeValueList = [atVal]
let myDic: [String: AWSDynamoDBCondition] = ["userid": condition]
let query = AWSDynamoDBQueryInput()
query.indexName = "userid-index"
query.tableName = "users"
query.keyConditions = myDic
query.limit = 1
dynamoDB.query(query).continueWithBlock {
(task: BFTask!) -> AnyObject! in
let results = task.result as AWSDynamoDBQueryOutput
let myResults = results.items
println("object: \(myResults.description)")
return nil
}
此操作的控制台输出为:
对象:[{
area=“{\n S=\”西汉普斯特德\“;\n}”;
name=“{\n S=\“Olly Mayes\”;\n}”;
userid=“{\n S=\”123456abc\”;\n}”;
}]
可以理解的是,使用AWS和Swift似乎没有太多的优先权,所以任何帮助都将不胜感激 问题的简单答案是:将返回的JSON字符串转换为Dictionary对象。 大概是这样的:
let data = jsonDataItem.dataUsingEncoding(NSUTF8StringEncoding)
if data != nil {
var error : NSError?
let dict = NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.AllowFragments, error: &error) as? NSDictionary
if let e = error {
...
} else {
...
}
但是,我强烈建议您查看更高级别的DynamoDB mapper类
当使用dynamodbmapper类时,您可以定义数据结构,并将其提供给。这是一个完整的示例,从表创建到表删除。该示例使用DynamoDB映射器插入、删除、扫描和查询表
首先,您需要初始化客户端SDK
let cp = AWSStaticCredentialsProvider(accessKey: "AK...", secretKey: "xxx")
let configuration = AWSServiceConfiguration(region: AWSRegionType.USEast1, credentialsProvider: cp)
AWSServiceManager.defaultServiceManager().setDefaultServiceConfiguration(configuration)
这只是一个样品。在代码中嵌入访问密钥和密钥不是一个好的做法。最佳做法是改用()
定义映射表中项目的类
class Item : AWSDynamoDBModel, AWSDynamoDBModeling {
var email : String = ""
var date : String = ""
var note : String = ""
var number : Double = 0.0
override init!() { super.init() }
required init!(coder: NSCoder!) {
fatalError("init(coder:) has not been implemented")
}
class func dynamoDBTableName() -> String! {
return "Demo"
}
class func hashKeyAttribute() -> String! {
return "email"
}
class func rangeKeyAttribute() -> String! {
return "date"
}
//required to let DynamoDB Mapper create instances of this class
override init(dictionary dictionaryValue: [NSObject : AnyObject]!, error: NSErrorPointer) {
super.init(dictionary: dictionaryValue, error: error)
}
//workaround to possible XCode 6.1 Bug : "Type NotificationAck" does not conform to protocol "NSObjectProtocol"
override func isEqual(anObject: AnyObject?) -> Bool {
return super.isEqual(anObject)
} }
self.createTable().continueWithSuccessBlock {(task: BFTask!) -> BFTask! in
NSLog("Create table - success")
return nil
}
func createTable() -> BFTask! {
let pt = AWSDynamoDBProvisionedThroughput()
pt.readCapacityUnits = 10
pt.writeCapacityUnits = 10
let emailAttr = AWSDynamoDBAttributeDefinition()
emailAttr.attributeName = "email"
emailAttr.attributeType = AWSDynamoDBScalarAttributeType.S
let dateAttr = AWSDynamoDBAttributeDefinition()
dateAttr.attributeName = "date"
dateAttr.attributeType = AWSDynamoDBScalarAttributeType.S
let emailKey = AWSDynamoDBKeySchemaElement()
emailKey.attributeName = "email"
emailKey.keyType = AWSDynamoDBKeyType.Hash
let dateKey = AWSDynamoDBKeySchemaElement()
dateKey.attributeName = "date"
dateKey.keyType = AWSDynamoDBKeyType.Range
let ct = AWSDynamoDBCreateTableInput()
ct.tableName = "Demo"
ct.provisionedThroughput = pt
ct.attributeDefinitions = [emailAttr, dateAttr]
ct.keySchema = [ emailKey, dateKey ]
NSLog("Creating table")
let client = AWSDynamoDB.defaultDynamoDB()
return client.createTable(ct)
}
self.deleteTable().continueWithSuccessBlock({ (task: BFTask!) -> BFTask! in
NSLog("Delete table - success")
return nil
})
func deleteTable() -> BFTask! {
let dt = AWSDynamoDBDeleteTableInput()
dt.tableName = "Demo"
NSLog("Deleting table")
let client = AWSDynamoDB.defaultDynamoDB()
return client.deleteTable(dt)
}
创建表格
class Item : AWSDynamoDBModel, AWSDynamoDBModeling {
var email : String = ""
var date : String = ""
var note : String = ""
var number : Double = 0.0
override init!() { super.init() }
required init!(coder: NSCoder!) {
fatalError("init(coder:) has not been implemented")
}
class func dynamoDBTableName() -> String! {
return "Demo"
}
class func hashKeyAttribute() -> String! {
return "email"
}
class func rangeKeyAttribute() -> String! {
return "date"
}
//required to let DynamoDB Mapper create instances of this class
override init(dictionary dictionaryValue: [NSObject : AnyObject]!, error: NSErrorPointer) {
super.init(dictionary: dictionaryValue, error: error)
}
//workaround to possible XCode 6.1 Bug : "Type NotificationAck" does not conform to protocol "NSObjectProtocol"
override func isEqual(anObject: AnyObject?) -> Bool {
return super.isEqual(anObject)
} }
self.createTable().continueWithSuccessBlock {(task: BFTask!) -> BFTask! in
NSLog("Create table - success")
return nil
}
func createTable() -> BFTask! {
let pt = AWSDynamoDBProvisionedThroughput()
pt.readCapacityUnits = 10
pt.writeCapacityUnits = 10
let emailAttr = AWSDynamoDBAttributeDefinition()
emailAttr.attributeName = "email"
emailAttr.attributeType = AWSDynamoDBScalarAttributeType.S
let dateAttr = AWSDynamoDBAttributeDefinition()
dateAttr.attributeName = "date"
dateAttr.attributeType = AWSDynamoDBScalarAttributeType.S
let emailKey = AWSDynamoDBKeySchemaElement()
emailKey.attributeName = "email"
emailKey.keyType = AWSDynamoDBKeyType.Hash
let dateKey = AWSDynamoDBKeySchemaElement()
dateKey.attributeName = "date"
dateKey.keyType = AWSDynamoDBKeyType.Range
let ct = AWSDynamoDBCreateTableInput()
ct.tableName = "Demo"
ct.provisionedThroughput = pt
ct.attributeDefinitions = [emailAttr, dateAttr]
ct.keySchema = [ emailKey, dateKey ]
NSLog("Creating table")
let client = AWSDynamoDB.defaultDynamoDB()
return client.createTable(ct)
}
self.deleteTable().continueWithSuccessBlock({ (task: BFTask!) -> BFTask! in
NSLog("Delete table - success")
return nil
})
func deleteTable() -> BFTask! {
let dt = AWSDynamoDBDeleteTableInput()
dt.tableName = "Demo"
NSLog("Deleting table")
let client = AWSDynamoDB.defaultDynamoDB()
return client.deleteTable(dt)
}
删除表格
class Item : AWSDynamoDBModel, AWSDynamoDBModeling {
var email : String = ""
var date : String = ""
var note : String = ""
var number : Double = 0.0
override init!() { super.init() }
required init!(coder: NSCoder!) {
fatalError("init(coder:) has not been implemented")
}
class func dynamoDBTableName() -> String! {
return "Demo"
}
class func hashKeyAttribute() -> String! {
return "email"
}
class func rangeKeyAttribute() -> String! {
return "date"
}
//required to let DynamoDB Mapper create instances of this class
override init(dictionary dictionaryValue: [NSObject : AnyObject]!, error: NSErrorPointer) {
super.init(dictionary: dictionaryValue, error: error)
}
//workaround to possible XCode 6.1 Bug : "Type NotificationAck" does not conform to protocol "NSObjectProtocol"
override func isEqual(anObject: AnyObject?) -> Bool {
return super.isEqual(anObject)
} }
self.createTable().continueWithSuccessBlock {(task: BFTask!) -> BFTask! in
NSLog("Create table - success")
return nil
}
func createTable() -> BFTask! {
let pt = AWSDynamoDBProvisionedThroughput()
pt.readCapacityUnits = 10
pt.writeCapacityUnits = 10
let emailAttr = AWSDynamoDBAttributeDefinition()
emailAttr.attributeName = "email"
emailAttr.attributeType = AWSDynamoDBScalarAttributeType.S
let dateAttr = AWSDynamoDBAttributeDefinition()
dateAttr.attributeName = "date"
dateAttr.attributeType = AWSDynamoDBScalarAttributeType.S
let emailKey = AWSDynamoDBKeySchemaElement()
emailKey.attributeName = "email"
emailKey.keyType = AWSDynamoDBKeyType.Hash
let dateKey = AWSDynamoDBKeySchemaElement()
dateKey.attributeName = "date"
dateKey.keyType = AWSDynamoDBKeyType.Range
let ct = AWSDynamoDBCreateTableInput()
ct.tableName = "Demo"
ct.provisionedThroughput = pt
ct.attributeDefinitions = [emailAttr, dateAttr]
ct.keySchema = [ emailKey, dateKey ]
NSLog("Creating table")
let client = AWSDynamoDB.defaultDynamoDB()
return client.createTable(ct)
}
self.deleteTable().continueWithSuccessBlock({ (task: BFTask!) -> BFTask! in
NSLog("Delete table - success")
return nil
})
func deleteTable() -> BFTask! {
let dt = AWSDynamoDBDeleteTableInput()
dt.tableName = "Demo"
NSLog("Deleting table")
let client = AWSDynamoDB.defaultDynamoDB()
return client.deleteTable(dt)
}
插入项目
self.insertSomeItems().continueWithBlock({
(task: BFTask!) -> BFTask! in
if (task.error != nil) {
NSLog(task.error.description)
} else {
NSLog("DynamoDB save succeeded")
}
return nil;
})
func insertSomeItems() -> BFTask! {
let mapper = AWSDynamoDBObjectMapper.defaultDynamoDBObjectMapper()
var item = Item()
item.email = "stormacq@amazon.com"
item.date = "20141101"
item.note = "This is item #1"
item.number = 1.0
let task1 = mapper.save(item)
item = Item()
item.email = "stormacq@amazon.com"
item.date = "20141102"
item.note = "This is item #2"
item.number = 2.0
let task2 = mapper.save(item)
item = Item()
item.email = "stormacq@amazon.lu"
item.date = "20141103"
item.note = "This is item #3"
item.number = 3.0
let task3 = mapper.save(item)
return BFTask(forCompletionOfAllTasks: [task1, task2, task3])
}
加载单个项目
self.load("stormacq@amazon.com", range:"20141101").continueWithSuccessBlock({ (task: BFTask!) -> BFTask! in
NSLog("Load one value - success")
let item = task.result as Item
print(item)
return nil
})
func load(hash: String, range: String) -> BFTask! {
let mapper = AWSDynamoDBObjectMapper.defaultDynamoDBObjectMapper()
return mapper.load(Item.self, hashKey: hash, rangeKey: range)
}
查询哈希和范围键
/*
keyConditions
http://docs.aws.amazon.com/AWSiOSSDK/latest/Classes/AWSDynamoDBQueryInput.html#//api/name/keyConditions
*/
let cond = AWSDynamoDBCondition()
let v1 = AWSDynamoDBAttributeValue(); v1.S = "20141101"
cond.comparisonOperator = AWSDynamoDBComparisonOperator.EQ
cond.attributeValueList = [ v1 ]
let c = [ "date" : cond ]
self.query("stormacq@amazon.com", keyConditions:c).continueWithSuccessBlock({ (task: BFTask!) -> BFTask! in
NSLog("Query multiple values - success")
let results = task.result as AWSDynamoDBPaginatedOutput
for r in results.items {
print(r)
}
return nil
})
func query(hash: String, keyConditions:[NSObject:AnyObject]) -> BFTask! {
let mapper = AWSDynamoDBObjectMapper.defaultDynamoDBObjectMapper()
let exp = AWSDynamoDBQueryExpression()
exp.hashKeyValues = hash
exp.rangeKeyConditions = keyConditions
return mapper.query(Item.self, expression: exp)
}
扫描项目(全表扫描)
如果您在美国东部1没有其他使用DynamoDB,则运行此示例不会产生任何相关费用,因为它将陷入困境。感谢您的回复。我两种方法都试过了,但都没有达到我想要的效果。第一个似乎失败了,因为返回的JSON实际上不是格式正确的JSON。如果可能的话,我想让对象映射器工作,你知道如果操作是“查询”而不是“保存”,这将如何工作吗?为了清楚起见,我想使用userid字段查询users表-这不是主索引,而是辅助索引-我想获取此用户的“区域”。是的,您也可以使用映射器进行查询。看:如果我今晚有时间,我会给你举个例子的。我已经试过几次了,但是运气不好!你能举个简单的例子吗?当我回到我的开发机器时,我将粘贴我已经完成的工作…这是一个纯粹的SWIFT错误,而不是AWS错误。这是因为您的task.result不包含值。。。你们桌上有“156”项吗?要避免该运行时错误,请使用条件转换:let item=task.result as?DBItem(请注意问号)我已经编写了一个关于使用AWS(包括DynamoDB)作为Swift应用程序后端的系列教程。