核心数据-实现一对一的自定义关系 [英] Core data - implementing a custom to one relationship

问题描述

我不确定这是否是一个愚蠢的问题：

我有一个托管对象A，而托管对象A与表B有多对一的关系。 / p>

我通过执行以下操作将关系A设置为B

  .Bobject = acopyOfB; 
  

哪个还可以。

我要为该关系编写自定义设置器。这样一来，我就可以根据B设置的值在A中设置一些只读属性。

所以我想填补空白：

 -（void）setBobject：（Bobject）theValue {
 
 
'差距'
 
} 
  

我很高兴能够设置自定义值，但是可以

解决方案

您将需要做类似的事情

 -（void）setBObject：（BObject *）theValue {
 [self willChangeValueForKey：@ bObject]; 
 [self setPrimitiveBObject：theValue]; 
 [self didChangeValueForKey：@ bObject]; 
 
 //做其他您需要在这里做的事情
} 
  

为避免编译器警告，您可以在 @implementation 指令之前声明以下内容（但要在 .m 文件中） ）：

  @interface MyManagedObjectSubClass（PrimitiveAccessors）
 
 @property（非原子，保留）BObject * nativeBObject ; 
 
 @end 
  

I am not sure if this is a dumb question:

I have an managed object A and managed object A has a many to one relationship with table B.

I set the relationship A to B by doing something like

 Aobject.Bobject=acopyOfB;

Which is fine.

I want to write a custom setter for that relationship. This is so I can setup some read only properties in A, based on the value that B gets set to.

So I want to fill in the gap:

    -(void) setBobject:(Bobject)theValue{


  'the gap'

  }

I am happy with being able to set my custom values, but can't find anywhere the correct syntax for setting the relationship within core data.

解决方案

You will need to do something like

- (void) setBObject:(BObject*)theValue {
  [self willChangeValueForKey:@"bObject"];
  [self setPrimitiveBObject:theValue];
  [self didChangeValueForKey:@"bObject"];

  // Do whatever else you need to do here
}

To avoid compiler warnings, you can declare the following before the @implementation directive (but in the .m file):

@interface MyManagedObjectSubClass (PrimitiveAccessors)

@property (nonatomic, retain) BObject* primitiveBObject;

@end

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