不允许更改核心数据关系，但最终允许删除子项

Question

我有一个包含两个实体'Parent'和'Child'的核心数据模型。 父母与孩子有多对多的关系，孩子与父母有一对一的关系。 我想防止在设置父项的情况下对子项中的父项关系进行更改。但是，应该允许删除孩子。

孩子的的setParent看起来是这样的：

- (void)setParent:(Parent *)parent { 
    if (self.parent) return; 
    [self willChangeValueForKey:@"parent"]; 
    [self setPrimitiveValue:parent forKey:@"parent"]; 
    [self didChangeValueForKey:@"parent"]; 
    } 

现在，这阻止了父母的变化，一旦它的设置，但在同一时间，它会阻止删除的孩子，因为的setParent被重新在删除期间两次将父项设置为零。

第一次在删除期间调用setParent，self.isDeleted为true。所以我可以对这种情况做出反应。但setParent在删除期间再次被调用，这一次self.isDeleted为false，我不知道如何知道某人是否尝试编辑父关系或是否发生删除。

我与MagicalRecord 2.30和删除调用的工作是这样的：

[MagicalRecord saveWithBlockAndWait:^(NSManagedObjectContext *localContext)  { 

    [sut MR_inContext:localContext]; 
    [sut MR_deleteEntityInContext:localContext]; 
}]; 

我看了所有的地方找到有关期间删除那些二传手呼吁一些信息，但没有运气。 所以任何帮助，将不胜感激。

编辑 我把一些NSLogs放到我的代码中，以便文档正在发生。删除实际上适用于这个代码，但我不知道所有这些调用的内容。下面是相关代码：

- (BOOL) MR_deleteEntityInContext:(NSManagedObjectContext *)context { 
    NSLog(@"|"); 
    NSLog(@"|"); 
    NSLog(@"----------------------------------"); 
    NSLog(@"| ***** starting delete... ***** |"); 
    NSLog(@"----------------------------------"); 
    NSLog(@"|"); 
    NSLog(@"|"); 
    return [super MR_deleteEntityInContext:context]; 
} 

- (void)setParent:(Parent *)parent { 
    NSLog(@"|"); 
    NSLog(@"--------------------------------------------------------------------------"); 
    NSLog(@"setParent has been called with parameter <%p>", parent); 
    NSLog(@"       self.parent is: %p", self.parent); 
    NSLog(@"self.isDeleted is: %hhd", self.isDeleted); 
    NSLog(@"   self.moc: %@", self.managedObjectContext); 
    NSLog(@"--------------------------------------------------------------------------"); 
    NSLog(@"|"); 
    if (!self.isDeleted && self.parent) return; 
    [self willChangeValueForKey:@"parent"]; 
    [self setPrimitiveValue:parent forKey:@"parent"]; 
    [self didChangeValueForKey:@"parent"]; 
} 

它产生以下输出：

---------------------------------- 
| ***** starting delete... ***** | 
---------------------------------- 
| 
| 
| 
-------------------------------------------------------------------------- 
setParent has been called with parameter <0x0> 
          self.parent is: 0x6080000a9cc0 
self.isDeleted is: 1 
      self.moc: <NSManagedObjectContext: 0x6000001c05a0> 
-------------------------------------------------------------------------- 
| 
| 
-------------------------------------------------------------------------- 
setParent has been called with parameter <0x0> 
          self.parent is: 0x6080000aa080 
self.isDeleted is: 0 
      self.moc: <NSManagedObjectContext: 0x6080001c0a50> 
-------------------------------------------------------------------------- 
| 
| 
-------------------------------------------------------------------------- 
setParent has been called with parameter <0x0> 
          self.parent is: 0x6080000aa080 
self.isDeleted is: 1 
      self.moc: <NSManagedObjectContext: 0x6080001c0a50> 
-------------------------------------------------------------------------- 
| 

Answer 1

这是我发现的。我已经改变了上面的代码来记录反向关系。

- (void)setParent:(Parent *)parent { 
    NSLog(@" "); 
    NSLog(@"--------------------------------------------------------------------------"); 
    NSLog(@"| setParent has been called with parameter <%p>", parent); 
    NSLog(@"|         self is: %p", self); 
    NSLog(@"|       self.parent is: %p", self.parent); 
    NSLog(@"|    parent.children contains: %p", [Parent MR_findFirstInContext:self.managedObjectContext].children.allObjects.firstObject); 
    NSLog(@"| self.isDeleted is: %hhd", self.isDeleted); 
    NSLog(@" "); 
    if (!self.isDeleted && self.parent) return; 
    if (self.isDeleted) [self setPrimitiveValue:nil forKey:@"parent"]; 
    [self willChangeValueForKey:@"parent"]; 
    [self setPrimitiveValue:parent forKey:@"parent"]; 
    [self didChangeValueForKey:@"parent"]; 
    NSLog(@"|- after setting the parent ..."); 
    NSLog(@"|-        self is: %p", self); 
    NSLog(@"|-       self.parent is: %p", self.parent); 
    NSLog(@"|-    parent.children contains: %p", [Parent MR_findFirstInContext:self.managedObjectContext].children.allObjects.firstObject); 
    NSLog(@"--------------------------------------------------------------------------"); 
} 

当我删除以下记录孩子：

---------------------------------- 
| ***** starting delete... ***** | 
---------------------------------- 
| 
| 

-------------------------------------------------------------------------- 
| setParent has been called with parameter <0x0> 
|         self is: 0x6000000a79e0 
|       self.parent is: 0x6000000a7a40 
|    parent.children contains: 0x6000000a79e0 
| self.isDeleted is: 1 

|- after setting the parent ... 
|-        self is: 0x6000000a79e0 
|-       self.parent is: 0x0 
|-    parent.children contains: 0x6000000a79e0 
-------------------------------------------------------------------------- 

-------------------------------------------------------------------------- 
| setParent has been called with parameter <0x0> 
|         self is: 0x6080000a8100 
|       self.parent is: 0x6080000a8160 
|    parent.children contains: 0x0 
| self.isDeleted is: 0 


-------------------------------------------------------------------------- 
| setParent has been called with parameter <0x0> 
|         self is: 0x6080000a8100 
|       self.parent is: 0x6080000a8160 
|    parent.children contains: 0x0 
| self.isDeleted is: 1 

|- after setting the parent ... 
|-        self is: 0x6080000a8100 
|-       self.parent is: 0x0 
|-    parent.children contains: 0x0 
-------------------------------------------------------------------------- 

所以，第一个和第三个时间设置器中删除名为，isDeleted是真实的。但在二传手的第二个电话isDeleted是错误的。 如果我在这一点测试反比关系，我发现它已被删除。这个测试对我来说已经足够了。它允许删除循环通过，同时允许运行setter，如果关系还没有被设置。

Answer 2

您可以设置parent到nil如果isDeleted是true，通过@Avi的建议。