Swift / CloudKit: After record changed, upload triggers "Service Record Changed"
<p><strong>I'm trying to add a CKReference to a record in cloud kit, but the attempt keeps triggering "Service Record Changed".</strong> From the console messages my println's have shown (console messages and code below), I'm uploading said record with 0 references, then when I attach the reference I'm seeing an attempt to upload the record with 1 reference. Then I'm getting the error.</p>

<p>As I understand it, <strong>"Service Record Changed" shouldn't be triggered because the values in the Reference List have changed (the record has an entire extra field).</strong> Even though I'm in development mode, I manually created key-value field for the Reference List, because the first record upload doesn't include the field when the reference list is empty (uploading an empty array causes another error). </p>

<p>I'll include code in order of relevance (you'll be able to see most of the println's) after the console messages. The whole project is on github and I can link to it or include more code if needed.</p>

<p>Relevant Console:</p>

<pre><code>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: &lt;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"&gt;
u!error for TestCrewParticipant
CKError: &lt;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"&gt;
passing the guard 
</code></pre>

<p>Code from CrewParticipant:</p>

<pre><code>/**
 * 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) }
}
</code></pre>

<p>generic code (which works for several other classes) where upload occurs:</p>

<pre><code>/**
 * 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&lt;T: Recordable&gt;
    (instanceConformingToRecordable: T, database: CKDatabase, completionHandler: (() -&gt; ())? = 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)")
        }            
    }
}
</code></pre>