使用 RESTkit 从 JSON 映射来自 NSManagedObject 的 NSString 数组答案

【问题标题】：Mapping array of NSString's from NSManagedObject from JSON using RESTkit使用 RESTkit 从 JSON 映射来自 NSManagedObject 的 NSString 数组
【发布时间】：2014-04-10 12:06:55
【问题描述】：

一些先决条件：

JSON 正文：

"returnCode":{“messages”[], "something":1}

应该映射到：

@interface ReturnCodeEntity : NSMutableObject

@property (nonatomic, retain) id messages; // Should be defined as Transformable?
@property (nonatomic, retain) NSString * something;

问题：

你好，我猜这是两个问题：

为核心数据实体中的“消息”数组定义正确的类型
使用 RKEntityMapping 类映射此数组

现在映射操作完成后出现异常：

2014-04-10 12:12:05.661 [4811:3f07] D restkit.object_mapping:RKMappingOperation.m:929 Finished mapping operation successfully...
2014-04-10 12:12:05.661 [4811:3f07] -[__NSDictionaryM _stateFlags]: unrecognized selector sent to instance 0x10990d0b0
2014-04-10 12:12:08.786 [4811:3f07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSDictionaryM _stateFlags]: unrecognized selector sent to instance 0x10990d0b0'
 First throw call stack:
(
    0   CoreFoundation                      0x0000000102af8495 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010285799e objc_exception_throw + 43
    2   CoreFoundation                      0x0000000102b8965d -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
    3   CoreFoundation                      0x0000000102ae9d8d ___forwarding___ + 973
    4   CoreFoundation                      0x0000000102ae9938 _CF_forwarding_prep_0 + 120
    5   CoreData                            0x00000001008ec8f8 -[NSRelationshipDescription(_NSInternalMethods) _nonPredicateValidateValue:forKey:inObject:error:] + 232
    6   CoreData                            0x00000001008eba27 -[NSManagedObject(_NSInternalMethods) _validateValue:forProperty:andKey:withIndex:error:] + 375
    7   CoreData                            0x00000001009651d7 -[NSManagedObject validateValue:forKey:error:] + 135
    8   Foundation                          0x0000000100f19ed5 -[NSObject(NSKeyValueCoding) validateValue:forKeyPath:error:] + 336
    9                                       0x0000000100212cb5 -[RKMappingOperation validateValue:atKeyPath:] + 341
    10                                      0x000000010021334d -[RKMappingOperation shouldSetValue:forKeyPath:usingMapping:] + 861
    11                                      0x00000001002177dd -[RKMappingOperation mapOneToOneRelationshipWithValue:mapping:] + 1661
    12                                      0x000000010021b14a -[RKMappingOperation applyRelationshipMappings] + 6186
    13                                      0x000000010021d2f6 -[RKMappingOperation main] + 4006
    14  Foundation                          0x0000000100f2bd34 -[__NSOperationInternal _start:] + 623
    15                                      0x000000010020ca5e -[RKMapperOperation mapRepresentation:toObject:atKeyPath:usingMapping:metadata:] + 1886
    16                                      0x000000010020b3ff -[RKMapperOperation mapRepresentation:atKeyPath:usingMapping:] + 1871
    17                                      0x000000010020dd75 -[RKMapperOperation mapRepresentationOrRepresentations:atKeyPath:usingMapping:] + 805
    18                                      0x000000010020e5a8 -[RKMapperOperation mapSourceRepresentationWithMappingsDictionary:] + 1944
    19                                      0x000000010020eef5 -[RKMapperOperation main] + 1365

在groups.google.com 上进行了讨论，但最终得到了解决方法。

感谢您的建议。

编辑

我在体内引入了台风。是的，这篇文章中缺少分号

{"returnCode":{"messages":[], "something":1}}

我对模型进行了一些更改，因此 ReturnCodeEntity 包含引用新类型 MessageEntity 的 NSSet，该类型将消息存储在“文本”属性中：

@interface ReturnCodeEntity : NSMutableObject

@property (nonatomic, retain) NSString * something;
@property (nonatomic, retain) NSSet *messages; // --> relationship 1 to many MessageEntitie's
@end

@interface ReturnCodeEntity (CoreDataGeneratedAccessors)

- (void)addMessagesObject:(MessageEntity *)value;
- (void)removeMessagesObject:(MessageEntity *)value;
- (void)addMessages:(NSSet *)values;
- (void)removeMessages:(NSSet *)values;
@end

@interface MessageEntity : NSMutableObject

@property (nonatomic, retain) NSString * text;
@property (nonatomic, retain) ReturnCodeEntity *returnCode; // --> relationship 1 to 1 ReturnCodeEntity
@end

我已经为 MessageEntity 创建了映射：

RKEntityMapping *mapping = [RKEntityMapping mappingForEntityForName:@"MessageEntity" inManagedObjectStore:managedObjectStore];
[mapping addPropertyMapping:[RKAttributeMapping attributeMappingFromKeyPath:nil toKeyPath:@"text"]];
mapping.identificationAttributes = @[ @"text" ];

... 并将其添加到 returnCodeEntityMapping 中

[returnCodeEntityMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"messages" toKeyPath:@"messages" withMapping:messageApiMapping]];

跟踪表明映射在层次结构中成功，但后来它在 RKMappingOperation.m 方法中崩溃 *- (BOOL)validateValue:(id *)value atKeyPath:(NSString )keyPath

success = [self.destinationObject validateValue:value forKeyPath:keyPath error:&validationError];

谢谢你的帮助。

【问题讨论】：

想必JSON实际上是{"returnCode":{“messages”:[], "something":1}} ?

标签： json core-data nsarray restkit nsmanagedobject

【解决方案1】：

我的问题是为 MessageEntity 映射而不是 RKAttributeMapping 实例化 RKObjectMapping。

这是因为我从另一个使用 [RKObjectMapping requestMapping] 的实体类中复制了代码（因为请求）。我必须补充一点（从 Restkit 用户的角度来看）使用 RKObjectMapping 进行请求是令人困惑的，即使在后台我不需要使用 RKAttributeMapping。我更喜欢这里一致的api（RKAttributeMapping）。但无论如何，Restkit 是避免手动解析/映射的好工具。

Wain 的这个解决方案很有用

RestKit: mapping JSON array of strings

【讨论】：