Objective c 核心数据与实体关系问题

在我的核心数据模型中，我有两个实体：

目录项

清查行动

InventoryItem具有以下属性：
属性：

@property (nonatomic, retain) NSNumber * allowsActions;
@property (nonatomic, retain) NSNumber * assetID;
@property (nonatomic, retain) NSNumber * inventoryObjectID;
@property (nonatomic, retain) NSString * objectDescription;
@property (nonatomic, retain) NSNumber * quantity;
@property (nonatomic, retain) NSNumber * retired;
@property (nonatomic, retain) NSString * serialNumber;

@property (nonatomic, retain) NSSet *action;

@property (nonatomic, retain) NSDate * actionDate;
@property (nonatomic, retain) NSNumber * actionID;
@property (nonatomic, retain) NSString * actionLongValue;
@property (nonatomic, retain) NSString * actionShortValue;
@property (nonatomic, retain) NSString * notes;
@property (nonatomic, retain) NSNumber * userActionID;
@property (nonatomic, retain) NSString * userAuthorizingAction;
@property (nonatomic, retain) NSString * userPerformingAction;
@property (nonatomic, retain) NSNumber * userPerformingActionExt;
@property (nonatomic, retain) NSNumber * inventoryObjectID;

关系：

@property (nonatomic, retain) NSNumber * allowsActions;
@property (nonatomic, retain) NSNumber * assetID;
@property (nonatomic, retain) NSNumber * inventoryObjectID;
@property (nonatomic, retain) NSString * objectDescription;
@property (nonatomic, retain) NSNumber * quantity;
@property (nonatomic, retain) NSNumber * retired;
@property (nonatomic, retain) NSString * serialNumber;

@property (nonatomic, retain) NSSet *action;

@property (nonatomic, retain) NSDate * actionDate;
@property (nonatomic, retain) NSNumber * actionID;
@property (nonatomic, retain) NSString * actionLongValue;
@property (nonatomic, retain) NSString * actionShortValue;
@property (nonatomic, retain) NSString * notes;
@property (nonatomic, retain) NSNumber * userActionID;
@property (nonatomic, retain) NSString * userAuthorizingAction;
@property (nonatomic, retain) NSString * userPerformingAction;
@property (nonatomic, retain) NSNumber * userPerformingActionExt;
@property (nonatomic, retain) NSNumber * inventoryObjectID;

InventoryAction具有以下属性 属性：

@property (nonatomic, retain) NSNumber * allowsActions;
@property (nonatomic, retain) NSNumber * assetID;
@property (nonatomic, retain) NSNumber * inventoryObjectID;
@property (nonatomic, retain) NSString * objectDescription;
@property (nonatomic, retain) NSNumber * quantity;
@property (nonatomic, retain) NSNumber * retired;
@property (nonatomic, retain) NSString * serialNumber;

@property (nonatomic, retain) NSSet *action;

@property (nonatomic, retain) NSDate * actionDate;
@property (nonatomic, retain) NSNumber * actionID;
@property (nonatomic, retain) NSString * actionLongValue;
@property (nonatomic, retain) NSString * actionShortValue;
@property (nonatomic, retain) NSString * notes;
@property (nonatomic, retain) NSNumber * userActionID;
@property (nonatomic, retain) NSString * userAuthorizingAction;
@property (nonatomic, retain) NSString * userPerformingAction;
@property (nonatomic, retain) NSNumber * userPerformingActionExt;
@property (nonatomic, retain) NSNumber * inventoryObjectID;

关系

@property (nonatomic, retain) InventoryItem *object;

现在您已经掌握了所有这些信息，我将告诉您，CoreData模型中存储的所有值都来自JSON格式的web服务。所有值都已正确存储

我遇到的问题是，当我从CoreData获取数据时，它只返回唯一的值

例如： 最后一个InventoryItem有6个与之关联的操作：

“”，

“”，

“看起来有点粘”

“哦，上帝……你为什么要对一个你恶心的无生命物体这样做”

“现在都粘糊糊了”

“一切看起来都很好”

由于1和2具有相同的值，因此它只检索值1、3、4、5和6

下面是我用来获取数据的代码：

- (void)loadDetails
{
    _fetchRequest = [[NSFetchRequest alloc] init];
    _entity = [NSEntityDescription entityForName:@"InventoryObject" inManagedObjectContext:[self managedObjectContext]];
    _sort = [NSSortDescriptor sortDescriptorWithKey:@"inventoryObjectID" ascending:YES];
    _sortDescriptors = [[NSArray alloc]initWithObjects:_sort, nil];

    [_fetchRequest setEntity:_entity];
    [_fetchRequest setSortDescriptors:_sortDescriptors];

    NSError *error;
    _fetchedObjects = [[self managedObjectContext] executeFetchRequest:_fetchRequest error:&error];
    for (InventoryItem *inventoryItem in _fetchedObjects) {
        NSLog(@"Object Description: %@", [inventoryItem valueForKey:@"objectDescription"]);
        NSLog(@"Object ID: %@", [inventoryItem valueForKey:@"inventoryObjectID"]);
        InventoryAction *action = (InventoryAction *)inventoryItem.action;
        NSLog(@"Action Long Value: %@", [action valueForKey:@"actionLongValue"]);
        NSLog(@"Notes: %@", [action valueForKey:@"notes"]);

    }
}

以下是JSON返回：

[{"MediaInventoryObjectsId":1,"AssetId":15,"Quantity":1,"SerialNumber":"R45DFL5","Description":"Test Camera 1","AllowActions":true,"Retired":false,"Actions":[{"MediaInventoryActionsId":3,"MediaInventoryObjectsId":1,"UserPerformingActionExt":4444,"UserActionId":1,"ActionDate":"2014-05-19T15:31:45.6","UserPerformingAction":"myersb","UserAuthorizingAction":"mccroskeyl","Notes":null,"ActionShortValue":"OUT","ActionLongValue":"Check Out"},{"MediaInventoryActionsId":4,"MediaInventoryObjectsId":1,"UserPerformingActionExt":4444,"UserActionId":2,"ActionDate":"2014-05-19T15:31:45.6","UserPerformingAction":"myersb","UserAuthorizingAction":"mccroskeyl","Notes":"everything looks good","ActionShortValue":"IN","ActionLongValue":"Check In"}]},{"MediaInventoryObjectsId":2,"AssetId":15,"Quantity":2,"SerialNumber":"IDKMYBFFJILL","Description":"Vanilla Ice Cream","AllowActions":true,"Retired":false,"Actions":[]},{"MediaInventoryObjectsId":3,"AssetId":15,"Quantity":1,"SerialNumber":"R2D23P0","Description":"Droid Bee Box","AllowActions":true,"Retired":false,"Actions":[{"MediaInventoryActionsId":5,"MediaInventoryObjectsId":3,"UserPerformingActionExt":4444,"UserActionId":1,"ActionDate":"2014-05-20T14:48:29.53","UserPerformingAction":"myersb","UserAuthorizingAction":"mccroskeyl","Notes":null,"ActionShortValue":"OUT","ActionLongValue":"Check Out"},{"MediaInventoryActionsId":6,"MediaInventoryObjectsId":3,"UserPerformingActionExt":4444,"UserActionId":2,"ActionDate":"2014-05-20T14:48:29.58","UserPerformingAction":"myersb","UserAuthorizingAction":"mccroskeyl","Notes":"everything looks good","ActionShortValue":"IN","ActionLongValue":"Check In"},{"MediaInventoryActionsId":7,"MediaInventoryObjectsId":3,"UserPerformingActionExt":5555,"UserActionId":1,"ActionDate":"2014-05-20T14:48:29.6","UserPerformingAction":"farmer","UserAuthorizingAction":"mccroskeyl","Notes":null,"ActionShortValue":"OUT","ActionLongValue":"Check Out"},{"MediaInventoryActionsId":8,"MediaInventoryObjectsId":3,"UserPerformingActionExt":5555,"UserActionId":2,"ActionDate":"2014-05-20T14:48:29.6","UserPerformingAction":"farmer","UserAuthorizingAction":"mccroskeyl","Notes":"its all slimy now","ActionShortValue":"IN","ActionLongValue":"Check In"},{"MediaInventoryActionsId":9,"MediaInventoryObjectsId":3,"UserPerformingActionExt":6666,"UserActionId":1,"ActionDate":"2014-05-20T14:48:29.61","UserPerformingAction":"intern1","UserAuthorizingAction":"mccroskeyl","Notes":"it looks kinda slimy","ActionShortValue":"OUT","ActionLongValue":"Check Out"},{"MediaInventoryActionsId":10,"MediaInventoryObjectsId":3,"UserPerformingActionExt":6666,"UserActionId":2,"ActionDate":"2014-05-20T14:48:29.62","UserPerformingAction":"intern1","UserAuthorizingAction":"mccroskeyl","Notes":"oh god....why would you do that to an inanimate object you sicko","ActionShortValue":"IN","ActionLongValue":"Check In"}]}]

---

我在某个地方读到，NSSet可能只带回唯一的记录。这是真的吗？如果是真的，那么关系的解决方案是什么：action是一个NSSet？

您的关系声明如下：

@property (nonatomic, retain) NSSet *action;

InventoryAction *action = (InventoryAction *)inventoryItem.action;

但您可以这样访问它：

@property (nonatomic, retain) NSSet *action;

InventoryAction *action = (InventoryAction *)inventoryItem.action;

那是不对的。

action

关系是一个包含

InventoryAction

实例的

NSSet

，而不是

InventoryAction

本身。即使您将其分配给一个

InventoryAction*

，您实际拥有的还是一个

NSSet

。然后你要这样做：

NSLog(@"Notes: %@", [action valueForKey:@"notes"]);

如果在

NSSet

上调用

valueForKey:

，它将返回该键在集合中对象的所有唯一值。在本例中，它返回集合中

InventoryAction

对象的

notes

属性的所有唯一值，这就是您看到的。如果要查找每个实例而不是每个唯一值，则需要以下内容：

NSSet *actions = inventoryItem.action;
for (InventoryAction *action in actions) {
    NSLog(@"Action note: %@", action.note);
}

[警告，以上内容刚刚输入到我的web浏览器中….]