Swift/CloudKit:更改记录后,上传触发"服务记录已更改"

Question

我正在尝试将CKReference添加到云工具包中的记录中,但尝试会一直触发"服务记录更改".从我的println显示的控制台消息(控制台消息和代码如下),我上传了带有0个引用的记录,然后当我附加引用时,我看到尝试上传带有1个引用的记录.然后我收到了错误.

据我了解,不应触发"服务记录已更改",因为参考列表中的值已更改(记录有一个完整的额外字段).即使我处于开发模式,我手动为参考列表创建了键值字段,因为当引用列表为空时,第一个记录上载不包括该字段(上传空数组会导致另一个错误).

我将在控制台消息之后按相关性顺序包含代码(您将能够看到大多数println).整个项目在github上,如果需要,我可以链接到它或包含更多代码.

相关控制台:

name was set
uploading TestCrewParticipant
with 0 references
if let projects
upload succeeded: TestCrewParticipant
attaching reference
adding TestVoyage:_d147aa657fbf2adda0c82bf30d0e29a9 from guard
references #: Optional(1)
uploading TestCrewParticipant
with 1 references
if let projects
success: 1
uploading TestCrewParticipant
with 1 references
if let projects
success: 1
local storage tested: TestCrewParticipant
u!error for TestCrewParticipant
CKError: <CKError 0x7fcbd05fa960: "Server Record Changed" (14/2004); server message = "record to insert already exists"; uuid = 96377029-341E-487C-85C3-E18ADE1119DF; container ID = "iCloud.com.lingotech.cloudVoyageDataModel">
u!error for TestCrewParticipant
CKError: <CKError 0x7fcbd05afb80: "Server Record Changed" (14/2004); server message = "record to insert already exists"; uuid = 3EEDE4EC-4BC1-4F18-9612-4E2C8A36C68F; container ID = "iCloud.com.lingotech.cloudVoyageDataModel">
passing the guard 

CrewParticipant的代码:

/**
 * This array stores a conforming instance's CKReferences used as database
 * relationships. Instance is owned by each record that is referenced in the
 * array (supports multiple ownership)
 */
var references: [CKReference] { return associatedProjects ?? [CKReference]() }

// MARK: - Functions

/**
 * This method is used to store new ownership relationship in references array,
 * and to ensure that cloud data model reflects such changes. If necessary, ensures
 * that owned instance has only a single reference in its list of references.
 */
mutating func attachReference(reference: CKReference, database: CKDatabase) {
print("attaching reference")
    guard associatedProjects != nil else {
print("adding \(reference.recordID.recordName) from guard")
        associatedProjects = [reference]
        uploadToCloud(database)
        return
    }
print("associatedProjects: \(associatedProjects?.count)")
    if !associatedProjects!.contains(reference) {
print("adding \(reference.recordID.recordName) regularly")
        associatedProjects!.append(reference)
        uploadToCloud(database)
    }
}

/**
 * An identifier used to store and recover conforming instances record.
 */
var recordID: CKRecordID { return CKRecordID(recordName: identifier) }

/**
 * This computed property generates a conforming instance's CKRecord (a key-value
 * cloud database entry). Any values that conforming instance needs stored should be
 * added to the record before returning from getter, and conversely should recover
 * in the setter.
 */
var record: CKRecord {
    get {
        let record = CKRecord(recordType: CrewParticipant.REC_TYPE, recordID: recordID)

        if let id = cloudIdentity { record[CrewParticipant.TOKEN] = id }

// There are several other records that are dealt with successfully here.

print("if let projects")
        // Referable properties
        if let projects = associatedProjects {
print("success: \(projects.count)")
            record[CrewParticipant.REFERENCES] = projects
        }

        return record
    }

    set { matchFromRecord(newValue) }
}

上传发生的通用代码(适用于其他几个类):

/**
 * This method uploads any instance that conforms to recordable up to the cloud. Does not check any 
 * redundancies or for any constraints before (over)writing.
 */
func uploadRecordable<T: Recordable>
    (instanceConformingToRecordable: T, database: CKDatabase, completionHandler: (() -> ())? = nil) {
print("uploading \(instanceConformingToRecordable.recordID.recordName)")
if let referable = instanceConformingToRecordable as? Referable { print("with \(referable.references.count) references") }
    database.saveRecord(instanceConformingToRecordable.record) { record, error in
        guard error == nil else {
print("u!error for \(instanceConformingToRecordable.recordID.recordName)")
            self.tempHandler = { self.uploadRecordable(instanceConformingToRecordable,
                                                       database: database,
                                                       completionHandler: completionHandler) }
            CloudErrorHandling.handleError(error!, errorMethodSelector: #selector(self.runTempHandler))
            return
        }
print("upload succeeded: \(record!.recordID.recordName)")
        if let handler = completionHandler { handler() }
    }
}

/**
 * This method comprehensiviley handles any cloud errors that could occur while in operation.
 *
 * error: NSError, not optional to force check for nil / check for success before calling method.
 *
 * errorMethodSelector: Selector that points to the func calling method in case a retry attempt is
 * warranted. If left nil, no retries will be attempted, regardless of error type.
 */
static func handleError(error: NSError, errorMethodSelector: Selector? = nil) {

    if let code: CKErrorCode = CKErrorCode(rawValue: error.code) {
        switch code {

        // This case requires a message to USER (with USER action to resolve), and retry attempt.
        case .NotAuthenticated:
            dealWithAuthenticationError(error, errorMethodSelector: errorMethodSelector)

        // These cases require retry attempts, but without error messages or USER actions.
        case .NetworkUnavailable, .NetworkFailure, .ServiceUnavailable, .RequestRateLimited, .ZoneBusy, .ResultsTruncated:
            guard errorMethodSelector != nil else { print("Error Retry CANCELED: no selector"); return }
            retryAfterError(error, selector: errorMethodSelector!)

        // These cases require no message to USER or retry attempts.
        default:
            print("CKError: \(error)")
        }            
    }
}

Answer 1

看起来你每次保存都会创建一个新的CKRecord.

CloudKit返回ServerRecordChanged告诉您服务器上已存在具有相同recordID的记录,并且您的保存尝试被拒绝,因为服务器记录的版本不同.

每条记录都有一个更改标记,允许服务器跟踪保存该记录的时间.保存记录时,CloudKit会将记录本地副本中的更改标记与服务器上的更改标记进行比较.如果两个标记不匹配 - 意味着存在潜在冲突 - 服务器使用[ CKModifyRecordsOperation的[ savePolicy ] 属性中的值来确定如何继续.

资料来源:CKModifyRecordsOperation参考

虽然您使用的是CKDatabase.saveRecord方便方法,但这仍然适用.默认的savePolicy是ifServerRecordUnchanged.

首先,我建议转换到CKModifyRecordsOperation,特别是如果要保存多个记录.它使您可以更好地控制该过程.

其次,在保存对现有记录的更改时,您需要从服务器更改CKRecord.您可以通过以下任何方式完成此操作:

1. 从CloudKit请求CKRecord,对该CKRecord进行更改,然后将其保存回CloudKit.
2. 使用CKRecord参考中的建议存储保存的CKRecord(保存后在完成块中返回的CKRecord),保留此数据,然后取消归档以获取CKRecord,您可以修改并保存到服务器.(这避免了一些网络往返请求服务器CKRecord.)

在本地存储记录

如果将记录存储在本地数据库中,请使用encodeSystemFields(with :)方法对记录的元数据进行编码和存储.元数据包含记录ID和更改标记,稍后需要将本地数据库中的记录与CloudKit存储的记录同步.

let record = ...

// archive CKRecord to NSData
let archivedData = NSMutableData()
let archiver = NSKeyedArchiver(forWritingWithMutableData: archivedData)
archiver.requiresSecureCoding = true
record.encodeSystemFieldsWithCoder(archiver)
archiver.finishEncoding()

// unarchive CKRecord from NSData
let unarchiver = NSKeyedUnarchiver(forReadingWithData: archivedData)  
unarchiver.requiresSecureCoding = true 
let unarchivedRecord = CKRecord(coder: unarchiver)

资料来源:CloudKit提示与技巧--WDDC 2015

请记住:ServerRecordChanged如果其他设备在您请求/上次保存并存储服务器记录后保存对记录的更改,您仍会遇到错误.您需要通过获取最新的服务器记录来处理此错误,并将更改重新应用于该CKRecord.