Restkit 对象映射给出空对象

Posted 2023-03-05

【中文标题】Restkit 对象映射给出空对象

【英文标题】：Restkit object mapping gives null objects

【发布时间】：2012-07-06 22:21:19

【问题描述】：

我有一个名为Contact 的实体（在Core Data 上），每个联系人都有一个与之相关的Neighborhood、User 和ContactOrigin 实体。 当我从服务器检索 JSON 数据时，我得到如下信息：

  "contact" : [
    
      "prospect" : 
        "pkProspect" : 21,
        "name" : "Test Contact",
        "email" : "[e-mail]",
        "phone" : "5555555555",
        "address" : "Test Avenue",
        "media" : 
          "pkMedia" : 3,
          "name" : "Referência Entrevista You Move"
        ,
        "neighborhood" : 
          "pkNeighborhood" : 15857,
          "name" : "Donwtown"
        
      ,
      "user" : 
        "firstName" : "John",
        "pkPerson" : 5,
        "lastName" : "Doe"
      
    
  ]

如您所见，我有一个联系人数组，每个联系人都有一个用户节点、一个社区节点和一个媒体节点（我将其用作数据库的来源）。 RestKit 似乎用这段代码正确地映射了这个：

// Getting the object manager.
RKObjectManager *objectManager = [RKObjectManager sharedManager];

// Relationship mappings.    
RKManagedObjectMapping *neighborhoodMapping = [RKManagedObjectMapping mappingForClass:[Neighborhood class] inManagedObjectStore:objectManager.objectStore];
neighborhoodMapping.primaryKeyAttribute = @"identifier";
[neighborhoodMapping mapKeyPath:@"pkNeighborhood" toAttribute:@"identifier"];

RKManagedObjectMapping *originMapping = [RKManagedObjectMapping mappingForClass:[ContactOrigin class] inManagedObjectStore:objectManager.objectStore];
originMapping.primaryKeyAttribute = @"identifier";
[originMapping mapKeyPath:@"pkMedia" toAttribute:@"identifier"];

RKManagedObjectMapping *userMapping = [RKManagedObjectMapping mappingForClass:[User class] inManagedObjectStore:objectManager.objectStore];
userMapping.primaryKeyAttribute = @"identifier";
[userMapping mapKeyPath:@"pkPerson" toAttribute:@"identifier"];

// Creating the contact mapping for the request.
RKManagedObjectMapping *contactMapping = [RKManagedObjectMapping mappingForClass:[Contact class] inManagedObjectStore:objectManager.objectStore];
contactMapping.primaryKeyAttribute = kContactFieldNameId;

[contactMapping mapKeyPath:@"prospect.neighborhood" toRelationship:@"addressNeighborhood" withMapping:neighborhoodMapping];
[contactMapping mapKeyPath:@"prospect.media" toRelationship:@"origin" withMapping:originMapping];
[contactMapping mapKeyPath:@"user" toRelationship:@"user" withMapping:userMapping];

[contactMapping connectRelationship:@"addressNeighborhood" withObjectForPrimaryKeyAttribute:@"identifier"];
[contactMapping connectRelationship:@"origin" withObjectForPrimaryKeyAttribute:@"identifier"];
[contactMapping connectRelationship:@"user" withObjectForPrimaryKeyAttribute:@"identifier"];

[contactMapping mapKeyPath:@"prospect.pkProspect" toAttribute:@"identifier"];
[contactMapping mapKeyPath:@"prospect.name" toAttribute:@"name"];
[contactMapping mapKeyPath:@"prospect.email" toAttribute:@"email"];
[contactMapping mapKeyPath:@"prospect.phone" toAttribute:@"phone"];
[contactMapping mapKeyPath:@"prospect.address" toAttribute:@"address"];

// Setting the result mapping.
[objectManager.mappingProvider setObjectMapping:contactMapping forKeyPath:@"contact"];
// Loading data.
[objectManager loadObjectsAtResourcePath:resourcePath usingBlock:^(RKObjectLoader *loader) 
    loader.delegate = self;
    loader.userData = delegate;
];

映射完成后，我收到以下消息（我只显示User 错误）：

2012-07-06 18:20:23.016 Contact Manager[8254:10c03] E restkit.core_data:RKManagedObjectStore.m:250 Core Data Save Error
                               NSLocalizedDescription:      The operation couldn’t be completed. (Cocoa error 1570.)
                               NSValidationErrorKey:            user
                               NSValidationErrorPredicate:  (null)
                               NSValidationErrorObject:
<Contact: 0x917dff0> (entity: Contact; id: 0x917e070 <x-coredata:///Contact/t9D9EE4AE-142A-45EC-88C1-E97833729D0C2> ; data: 
    address = "Test Avenue";
    addressNeighborhood = "0x918b5b0 <x-coredata://6E5AB6F3-AFF4-460E-A37D-285A105178F0/Neighborhood/p21>";
    email = "[e-mail]";
    identifier = 21;
    name = "Test Contact";
    origin = nil;
    phone = 5555555555;
    user = nil;
)
2012-07-06 18:20:23.024 Contact Manager[8254:10c03] E restkit.core_data:RKManagedObjectLoader.m:167 Failed to save managed object context after mapping completed: The operation couldn’t be completed. (Cocoa error 1560.)

如您所见，origin 和 user 均为 null，当我尝试将其保存在 Core Data 时，这会导致错误，因为这些字段是必需的，但如果我们查看来自RestKit 我们会看到那些对象已经被正确解析并且实际上它们存在于数据库中。

2012-07-06 18:20:22.938 Contact Manager[8254:10c03] D restkit.object_mapping:RKObjectMappingOperation.m:636 Starting mapping operation...
2012-07-06 18:20:22.940 Contact Manager[8254:10c03] T restkit.object_mapping:RKObjectMappingOperation.m:637 Performing mapping operation: RKObjectMappingOperation for 'User' object. Mapping values from object 
    firstName = John;
    lastName = Doe;
    pkPerson = 5;
 to object <User: 0x5ca9d60> (entity: User; id: 0xc5aa7a0 <x-coredata://6E5AB6F3-AFF4-460E-A37D-285A105178F0/User/p1> ; data: 
    contacts = "<relationship fault: 0xc5ab580 'contacts'>";
    email = "[e-mail]";
    identifier = 5;
    ip = "0.0.0.0";
    isLoggedIn = 1;
    language = "en";
    name = "John Doe";
    password = 4badaee57fed5610012a296273158f5f;
) with object mapping <RKManagedObjectMapping:0x5ca78b0 objectClass=User keyPath mappings => (
    "RKObjectKeyPathMapping: pkPerson => identifier"
)>
2012-07-06 18:20:22.942 Contact Manager[8254:10c03] T restkit.object_mapping:RKObjectMappingOperation.m:330 Mapping attribute value keyPath 'pkPerson' to 'identifier'
2012-07-06 18:20:22.943 Contact Manager[8254:10c03] D restkit.object_mapping:RKObjectPropertyInspector.m:107 Cached property names and types for Class 'User': 
    accessibilityHint = NSString;
    accessibilityLabel = NSString;
    accessibilityLanguage = NSString;
    accessibilityValue = NSString;
    contacts = NSSet;
    email = NSString;
    identifier = NSNumber;
    ip = NSString;
    isLoggedIn = NSNumber;
    language = NSString;
    name = NSString;
    password = NSString;

2012-07-06 18:20:22.944 Contact Manager[8254:10c03] T restkit.object_mapping:RKObjectMappingOperation.m:347 Skipped mapping of attribute value from keyPath 'pkPerson to keyPath 'identifier' -- value is unchanged (5)
2012-07-06 18:20:22.946 Contact Manager[8254:10c03] D restkit.object_mapping:RKObjectMappingOperation.m:643 Finished mapping operation successfully...
2012-07-06 18:20:22.966 Contact Manager[8254:10c03] T restkit.object_mapping:RKObjectMappingOperation.m:597 Mapped relationship object from keyPath 'user' to 'user'. Value: <User: 0x5ca9d60> (entity: User; id: 0xc5aa7a0 <x-coredata://6E5AB6F3-AFF4-460E-A37D-285A105178F0/User/p1> ; data: 
    contacts = "<relationship fault: 0xc5ab580 'contacts'>";
    email = "[e-mail]";
    identifier = 5;
    ip = "0.0.0.0";
    isLoggedIn = 1;
    language = "pt_BR";
    name = "John Doe";
    password = 4badaee57fed5610012a296273158f5f;
)
2012-07-06 18:20:22.968 Contact Manager[8254:10c03] D restkit.object_mapping:RKObjectMappingOperation.m:643 Finished mapping operation successfully...

所以，我的问题是，如果解析器在数据库中找到这些对象，为什么 user 和 origin 为空？映射有什么问题吗？

【参考方案1】：

经过大量调试，我找到了修复它的方法。首先，我对每个对象都使用相同的主键 (@"identifier")，这弄乱了映射。

在那之后，我删除了[contactMapping connectRelationship:withObjectForPrimaryKeyAttribute:]，因为它不再需要，现在一切似乎都正常了。