ios - CoreData严重应用错误: Entity is not key value coding-compliant

Question

我是 CoreData 和 Restkit 的新手，遇到以下错误时遇到了很多麻烦。

我正在使用 restkit 来解析从 Foursquare 返回的一些地点。不幸的是我一直收到这个错误:

2013-07-12 16:12:46.369 FlokMobile[5903:c07] CoreData: error: Serious application error.  Exception was caught during Core Data change processing.  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  [<FoursquareVenue 0x1ec5fb00> valueForUndefinedKey:]: the entity Venue is not key value coding-compliant for the key "distance". with userInfo {
    NSTargetObjectUserInfoKey = "<FoursquareVenue: 0x1ec5fb00> (entity: Venue; id: 0xb472c10 <x-coredata://EAB387D9-C6CB-4873-84C5-1C32E137FFE9/Venue/p49> ; data: {\n    canonicalUrl = \"https://foursquare.com/v/sams-cable-car-lounge/5171ef7b498e4035a7f7a371\";\n    location = \"0xb477860 <x-coredata://EAB387D9-C6CB-4873-84C5-1C32E137FFE9/Location/p30>\";\n    name = \"Sam's Cable Car Lounge\";\n    venueID = 5171ef7b498e4035a7f7a371;\n})";
    NSUnknownUserInfoKey = distance;
}
2013-07-12 16:12:46.370 FlokMobile[5903:c07] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<FoursquareVenue 0x1ec5fb00> valueForUndefinedKey:]: the entity Venue is not key value coding-compliant for the key "distance".'
*** First throw call stack:
(0x1e42012 0x1c67e7e 0x1ecafb1 0x24d1d4 0x168000b 0x1e8fc4 0x169e247 0x1738c62 0x2af8a5 0x2aa735 0x2ad011 0x17284f9 0x1e9c0c5 0x1df6efa 0x165cbb2 0x1bf163 0x258d2f 0x1ba596 0x1b9869 0x1e6558 0x25b025 0x1e0cc1 0x2697731 0x26a6014 0x26967d5 0x1de8af5 0x1de7f44 0x1de7e1b 0x28dd7e3 0x28dd668 0xbabffc 0x2e7d 0x2da5)
libc++abi.dylib: terminate called throwing an exception

这是我用来设置键映射的代码:

// Setup Restkit for Foursquare

//Setup mapping for response
NSError *error = nil;
NSURL *modelURL = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"FoursquareModel" ofType:@"momd"]];
//mutableCopy might not be necessary
NSManagedObjectModel *managedObjectModel = [[[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL] mutableCopy];
RKManagedObjectStore *managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:managedObjectModel];

//Initialize Core Data stack
[managedObjectStore createPersistentStoreCoordinator];

NSPersistentStore __unused *persistentStore = [managedObjectStore addInMemoryPersistentStore:&error];
NSAssert(persistentStore, @"Failed to add persistent store: %@", error);

[managedObjectStore createManagedObjectContexts];

//Set default store shared instance
[RKManagedObjectStore setDefaultStore:managedObjectStore];

//Configure Object Manager
RKObjectManager *objectManager = [RKObjectManager managerWithBaseURL:[NSURL URLWithString:@"https://api.foursquare.com/v2/"]];
objectManager.managedObjectStore = managedObjectStore;

[RKObjectManager setSharedManager:objectManager];

RKEntityMapping *venueMapping = [RKEntityMapping mappingForEntityForName:@"Venue" inManagedObjectStore:managedObjectStore];
RKEntityMapping *locationMapping = [RKEntityMapping mappingForEntityForName:@"Location" inManagedObjectStore:managedObjectStore];

[venueMapping addAttributeMappingsFromDictionary:@{
 @"name":         @"name",
 @"id":           @"venueID",
 @"canonicalUrl": @"canonicalUrl"}];
venueMapping.identificationAttributes = @[@"venueID"];

[locationMapping addAttributeMappingsFromArray:@[ @"address",@"cc",@"city",@"country",@"crossStreet",@"distance",@"lat",@"lng",
                                     @"postalCode",@"state"]];

//[venueMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"location" toKeyPath:@"location" withMapping:locationMapping]];
[venueMapping addRelationshipMappingWithSourceKeyPath:@"response.venues.location" mapping:locationMapping];


RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor
                                            responseDescriptorWithMapping:venueMapping
                                            pathPattern:nil
                                            keyPath:@"response.venues"
                                            statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

[objectManager addResponseDescriptor:responseDescriptor];

还有我的 CoreData 模型:

每次我运行该应用程序时，它总是无法对相同的 key 进行编码。它能够加载 field 并将键映射到 field 实体。我认为我处理 Venue 和 Location 实体之间关系的方式可能存在问题。

这是我得到的 JSON 的样子:

{
  "meta" : {
    "code" : 200
  },
  "response" : {
    "venues" : [
      {
        "id" : "40bbc700f964a520b1001fe3",
        "categories" : [
          {
            "pluralName" : "Plazas",
            "primary" : true,
            "shortName" : "Plaza",
            "id" : "4bf58dd8d48988d164941735",
            "name" : "Plaza",
            "icon" : {
              "prefix" : "https://foursquare.com/img/categories_v2/parks_outdoors/plaza_",
              "suffix" : ".png"
            }
          }
        ],
        "stats" : {
          "checkinsCount" : 75856,
          "usersCount" : 40342,
          "tipCount" : 176
        },
        "venuePage" : {
          "id" : "34303229"
        },
        "storeId" : "",
        "contact" : {
          "phone" : "4157817880",
          "formattedPhone" : "(415) 781-7880",
          "twitter" : "unionsquaresf"
        },
        "hereNow" : {
          "groups" : [],
          "count" : 0
        },
        "verified" : true,
        "url" : "http://visitunionsquaresf.com",
        "referralId" : "v-1373553758",
        "restricted" : true,
        "location" : {
          "address" : "Union Square Park",
          "city" : "San Francisco",
          "distance" : 68,
          "postalCode" : "94108",
          "crossStreet" : "btwn Post, Stockton, Geary & Powell St.",
          "country" : "United States",
          "lat" : 37.787750172585,
          "lng" : -122.40762822536455,
          "state" : "CA",
          "cc" : "US"
        },
        "canonicalUrl" : "https://foursquare.com/v/union-square/40bbc700f964a520b1001fe3",
        "specials" : {
          "count" : 0,
          "items" : []
        },

Answer 1

所以这就是我想出的:Restkit，出于某种奇怪的原因正在寻找实体“地点”中的关键“距离”

“距离”不是从 Foursquare 收到的 JSON 中的属性，也没有通过代码明确映射到任何地方。

我通过将“distance”键添加到“venue”实体来临时解决了眼前的问题。我不知道为什么会这样，以后可能会有一些奇怪的含义。

如果有人能进一步阐明这个问题，我将不胜感激。 希望我在我的代码中做错了什么，我只是没有看到它!

编辑:即使有 Blake 的建议，我还是遇到了同样的错误。