删除魔法记录导入时的孤立对象

Question

magicrecord 中有内置的东西来处理孤儿吗？例如，如果我加载以下 JSON 数据...

[
  { "_id"   : "b1", "name"  : "brandA"},
  { "_id"   : "b2", "name"  : "brandB"},
  { "_id"   : "b3", "name"  : "brandC"}
]

然后数据被更新，brandC 被删除

[
  { "_id"   : "b1", "name"  : "brandA"},
  { "_id"   : "b2", "name"  : "brandB"}
]

更重要的是，如何删除孤立的嵌套对象，例如下面的productB

[
  { "_id"   : "b1", 
    "name"  : "brandA"
    "products" : [
        {"_id" : "p1", "name" : "productA" },
        {"_id" : "p2", "name" : "productB" }
     ]
  },
  { "_id"   : "b2", 
    "name"  : "brandB"
    "products" : [
        {"_id" : "p3", "name" : "productC" },
        {"_id" : "p4", "name" : "productD" }
     ]
  }
]

Answer 1

想通了，但如果有人想提出更好的解决方案，请这样做。

在加载时移除“Level 0”上的孤儿

NSArray *newdata   =  [];//AN ARRAY OF NEW DATA
NSArray *idList         = [newdata valueForKey:@"_id"];
NSPredicate *predicate  = [NSPredicate predicateWithFormat:@"NOT(_id IN %@)", idList];
[MRBrand MR_deleteAllMatchingPredicate:predicate];
[[NSManagedObjectContext MR_defaultContext] MR_saveToPersistentStoreAndWait];

删除托管对象内“级别 1”上的嵌套孤儿

-(void)willImport:(id)data{
    NSArray *idList         = [data[@"products"] valueForKey:@"_id"];
    NSPredicate *predicate  = [NSPredicate predicateWithFormat:@"NOT(pid IN %@) AND brand.bid == %@", idList, self.bid];
    [Product MR_deleteAllMatchingPredicate:predicate inContext:self.managedObjectContext];
}

在 willImport 中的品牌实体上，我们正在搜索与新数据不匹配的产品 ID 并将其删除。