RestKit对象映射与外键的关系 [英] RestKit Object Mapping relationships with foreign keys

问题描述

可以RestKit连接关系而不存储外键作为属性，即直接从JSON中的关键字？

特别是，我有一个工作has_many客房关系。房间的JSON不包含作业，而是两者分别加载：

   -  job：{
 id ：1，
 name：John
} 
 
  -  room：{
 id：4，
 job_id：1，
 name ：spare bedroom
} 
  

作业在房间之前加载。

我的CoreData模型，Job有

的属性

  @interface作业：NSManagedObject 
 @property（nonatomic，retain）NSNumber * identifier; 
 @property（nonatomic，retain）NSString * name; 
 @property（nonatomic，retain）NSSet * rooms; 
 @end 
 
 @interface房间：NSManagedObject 
 @property（nonatomic，retain）NSNumber * identifier; 
 @property（nonatomic，retain）NSString * name; 
 @property（nonatomic，retain）Job * job; 
 @end 
  

目前我添加了一个 @property strong）NSNumber * jobID; 到Room，其中 @synthesize 。

  JobMapping：
 mapping = [RKManagedObjectMapping mappingForClass：[Job class]]; 
 [mapping setPrimaryKeyAttribute：@identifier]; 
 
 [mapping mapAttributes：@name，nil]; 
 [mapping mapKeyPath：@idtoAttribute：@identifier]; 
 
 [mapping mapRelationship：@roomswithMapping：[Room objectMapping]]; 
 
 
 
 RoomMapping 
 mapping = [RKManagedObjectMapping mappingForClass：[Room class]]; 
 [mapping setPrimaryKeyAttribute：@identifier]; 
 
 [mapping mapAttributes：@name，nil]; 
 [mapping mapKeyPath：@idtoAttribute：@identifier]; 
 [mapping mapKeyPath：@job_idtoAttribute：@jobID]; 
 
 [mapping mapRelationship：@jobwithMapping：[Job objectMapping]]; 
 
 [mapping connectRelationship：@jobwithObjectForPrimaryKeyAttribute：@jobID]; 
  

我想知道如果没有额外的jobID属性， / strong>我不想有一个jobID属性在CoreData xcdatamodeld - 它是多余的，因为关系涵盖了。

此外，如果我重建NSManagedObjects，需要重新添加jobID属性，这是冗长乏味的。我不能告诉restkit通过JSON中的job_id keypath将房间连接到相应的作业？

如果我删除该属性， mapKeyPath：@job_id行，并将最后一行更改为 [mapping connectRelationship：@jobwithObjectForPrimaryKeyAttribute：@job_id]; 我得到

 实体Room不是键值编码符合键job_id。 
  

解决方案

我会让JobId在核心数据中是一个瞬时值，

该集合会将关系设置为self.job = methodToReturnObjectMatchingJobId （这将被rest kit）

get会返回self.job.identifier

如果你不使用mogenerator

下面是我如何做的示例代码：

   - （void）setClaimId：（NSNumber *）claimId {
 Claim * propertyClaim = [claim listItemFromId：[claimId intValue] withContext：self.managedObjectContext]; 
 
 self.claim = propertyClaim; 
} 
  - （NSNumber *）claimId {
 
 return self.claim.referenceId; 
} 
  

其中listItemFromId是一个基于id返回对象的简单查询。 / p>

Can RestKit connect a relationship without storing the foreign key as an attribute, i.e., directly from the keypath in the JSON?

In particular, I've got a Job has_many Rooms relationship. The room's JSON doesn't contain the job, rather, both are loaded separately:

- job: {
    id: 1,
    name: "John"
}

- room: {
    id: 4,
    job_id: 1,
    name: "spare bedroom"
}

The Job is loaded before the Room.

My CoreData models, Job has properties for

@interface Job : NSManagedObject
@property (nonatomic, retain) NSNumber * identifier;
@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) NSSet *rooms;
@end

@interface Room : NSManagedObject
@property (nonatomic, retain) NSNumber * identifier;
@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) Job *job;
@end

Currently I add a @property (nonatomic, strong) NSNumber *jobID; to Room, which I @synthesize.

JobMapping:
    mapping = [RKManagedObjectMapping mappingForClass:[Job class]];
    [mapping setPrimaryKeyAttribute:@"identifier"];

    [mapping mapAttributes:@"name", nil];
    [mapping mapKeyPath:@"id" toAttribute:@"identifier"];

    [mapping mapRelationship:@"rooms" withMapping:[Room objectMapping]];



RoomMapping
    mapping = [RKManagedObjectMapping mappingForClass:[Room class]];
    [mapping setPrimaryKeyAttribute:@"identifier"];

    [mapping mapAttributes:@"name", nil];
    [mapping mapKeyPath:@"id" toAttribute:@"identifier"];
    [mapping mapKeyPath:@"job_id" toAttribute:@"jobID"];

    [mapping mapRelationship:@"job" withMapping:[Job objectMapping]];

    [mapping connectRelationship:@"job" withObjectForPrimaryKeyAttribute:@"jobID"];

I was wondering if there's a way I can do this without the extra jobID property? I don't want to have a jobID attribute in the CoreData xcdatamodeld - it's redundant, as the relationship covers that.

Also if I rebuild the NSManagedObjects, I need to re-add the jobID property, which is tedious. Can't I tell restkit to connect the Room to its corresponding Job via the job_id keypath in the JSON?

If I remove the property, the mapKeyPath:@"job_id" line, and change the last line to [mapping connectRelationship:@"job" withObjectForPrimaryKeyAttribute:@"job_id"]; I get

the entity Room is not key value coding-compliant for the key "job_id".

解决方案

I would make JobId a transient value in core data, and write a custom set and get for it.

The set would set the relationship to self.job=methodToReturnObjectMatchingJobId (this would be used by rest kit)

The get would return self.job.identifier

If you are not using mogenerator, I would suggest you have a look at it for all your core data needs.

Below is sample code of how i did it:

-(void) setClaimId:(NSNumber *)claimId{
     Claim *propertyClaim=[Claim listItemFromId:[claimId intValue] withContext:self.managedObjectContext]; 

    self.claim=propertyClaim; 
}
-(NSNumber*) claimId{

  return self.claim.referenceId;
}

where listItemFromId is a simple query that returns the object based on the id.

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