在Swift中插入一个To-One关系的NSManagedObject

Question

在Xcode 6b3上使用Swift时，我很难简单地插入一个具有一对一关系的NSManagedObject。

我把我的代表GitHub，但失败的代码(在SwiftCoreDataRelationshipReproTests.swift的testSwiftToOne单元测试方法)归结为:

let momURL : NSURL = NSBundle.mainBundle().URLForResource("SwiftCoreDataRelationshipRepro",
    withExtension: "momd")
let mom : NSManagedObjectModel = NSManagedObjectModel(contentsOfURL: momURL)
let psc : NSPersistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: mom);
let ps : NSPersistentStore = psc.addPersistentStoreWithType(
    NSInMemoryStoreType,
    configuration: nil,
    URL: nil,
    options: nil,
    error: nil)
let moc : NSManagedObjectContext = NSManagedObjectContext()
moc.persistentStoreCoordinator = psc
// This throws an NSInvalidArgumentException: "An NSManagedObject of class 'NSManagedObject' must have a valid NSEntityDescription."
NSManagedObject(
            entity: NSEntityDescription.entityForName("Pet", inManagedObjectContext: moc),
            insertIntoManagedObjectContext: moc)

看起来应该行得通。没有什么棘手。

我非常相似的具有多对多关系的Person实体可以用Swift正确插入(并保存)(通过testSwiftToMany测试证明)。更复杂的Objective-C版本也成功使用相同的数据模型(通过testObjcToOneAndToMany测试)。

下面是整个例外:

file:///%3Cunknown%3E: test failure: -[SwiftCoreDataRelationshipReproTests testSwiftToOne()] failed: failed: caught "NSInvalidArgumentException", "An NSManagedObject of class 'NSManagedObject' must have a valid NSEntityDescription."
(
    0   CoreFoundation                      0x00007fff8dd6525c __exceptionPreprocess + 172
    1   libobjc.A.dylib                     0x00007fff84ce5e75 objc_exception_throw + 43
    2   CoreData                            0x00007fff8765dd16 -[NSManagedObject initWithEntity:insertIntoManagedObjectContext:] + 550
    3   SwiftCoreDataRelationshipReproTests 0x0000000100394d4a _TTOFCSo15NSManagedObjectcfMS_FT6entityGSQCSo19NSEntityDescription_30insertIntoManagedObjectContextGSQCSo22NSManagedObjectContext__S_ + 42
    4   SwiftCoreDataRelationshipReproTests 0x00000001003946bd _TFCSo15NSManagedObjectCfMS_FT6entityGSQCSo19NSEntityDescription_30insertIntoManagedObjectContextGSQCSo22NSManagedObjectContext__S_ + 93
    5   SwiftCoreDataRelationshipReproTests 0x0000000100393450 _TFC35SwiftCoreDataRelationshipReproTests35SwiftCoreDataRelationshipReproTests14testSwiftToOnefS0_FT_T_ + 816
    6   SwiftCoreDataRelationshipReproTests 0x00000001003934c2 _TToFC35SwiftCoreDataRelationshipReproTests35SwiftCoreDataRelationshipReproTests14testSwiftToOnefS0_FT_T_ + 34
    7   CoreFoundation                      0x00007fff8dc50a5c __invoking___ + 140
    8   CoreFoundation                      0x00007fff8dc508c4 -[NSInvocation invoke] + 308
    9   XCTest                              0x00000001003b023a -[XCTestCase invokeTest] + 253
    10  XCTest                              0x00000001003b03ac -[XCTestCase performTest:] + 142
    11  XCTest                              0x00000001003b8ad0 -[XCTest run] + 257
    12  XCTest                              0x00000001003af68b -[XCTestSuite performTest:] + 379
    13  XCTest                              0x00000001003b8ad0 -[XCTest run] + 257
    14  XCTest                              0x00000001003af68b -[XCTestSuite performTest:] + 379
    15  XCTest                              0x00000001003b8ad0 -[XCTest run] + 257
    16  XCTest                              0x00000001003af68b -[XCTestSuite performTest:] + 379
    17  XCTest                              0x00000001003b8ad0 -[XCTest run] + 257
    18  XCTest                              0x00000001003acc8f __25-[XCTestDriver _runSuite]_block_invoke + 56
    19  XCTest                              0x00000001003b773d -[XCTestObservationCenter _observeTestExecutionForBlock:] + 162
    20  XCTest                              0x00000001003acbc8 -[XCTestDriver _runSuite] + 269
    21  XCTest                              0x00000001003ad34a -[XCTestDriver _checkForTestManager] + 551
    22  XCTest                              0x00000001003bb879 +[XCTestProbe runTests:] + 175
    23  Foundation                          0x00007fff8e0aacb7 __NSFireDelayedPerform + 333
    24  CoreFoundation                      0x00007fff8dccc494 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 20
    25  CoreFoundation                      0x00007fff8dccbfcf __CFRunLoopDoTimer + 1151
    26  CoreFoundation                      0x00007fff8dd3d5aa __CFRunLoopDoTimers + 298
    27  CoreFoundation                      0x00007fff8dc87755 __CFRunLoopRun + 1525
    28  CoreFoundation                      0x00007fff8dc86f25 CFRunLoopRunSpecific + 309
    29  HIToolbox                           0x00007fff8e566a0d RunCurrentEventLoopInMode + 226
    30  HIToolbox                           0x00007fff8e566685 ReceiveNextEventCommon + 173
    31  HIToolbox                           0x00007fff8e5665bc _BlockUntilNextEventMatchingListInModeWithFilter + 65
    32  AppKit                              0x00007fff8538e26e _DPSNextEvent + 1434
    33  AppKit                              0x00007fff8538d8bb -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 122
    34  AppKit                              0x00007fff853819bc -[NSApplication run] + 553
    35  AppKit                              0x00007fff8536c7a3 NSApplicationMain + 940
    36  SwiftCoreDataRelationshipRepro      0x000000010000ad55 top_level_code + 37
    37  SwiftCoreDataRelationshipRepro      0x000000010000ad8a main + 42
    38  libdyld.dylib                       0x00007fff861115fd start + 1
)

Answer 1

所以我无法解决这个问题，但我认为我把它缩小到框架或Swift的错误。使用entityForName相当于直接从managedObjectModel中获取实体，所以我试图这样做:

let entities = moc.persistentStoreCoordinator.managedObjectModel.entitiesByName;
let keys = Array(entities.keys)
let petVar : String = keys[1] as String
let isEqual1 = (petVar == "Pet") // true
let isEqual2 = (petVar.hashValue == "Pet".hashValue) // true
let result1 = entities["Pet"] // nil
let result2 = entities[petVar] // non-nil
let result3 = entities.bridgeToObjectiveC().objectForKey("Pet".bridgeToObjectiveC()) // nil
let result4 = entities.bridgeToObjectiveC().objectForKey(petVar.bridgeToObjectiveC()) // non-nil
// Doesn't Pass
XCTAssertNotNil(NSEntityDescription.entityForName("Pet", inManagedObjectContext: moc));
// Passes
XCTAssertNotNil(NSEntityDescription.entityForName(petVar, inManagedObjectContext: moc));

它适用于从字典中取出的键，但不适用于与键等效的字符串(即使哈希值相同)。

我认为这非常明确地表明，要么在框架中，要么在Swift本身存在bug。我正在运行Xcode (6b3)和10.9.4