NSArray valueForKey返回NSNull？(NSArray valueForKey returning NSNull?)

NSArray valueForKey返回NSNull？(NSArray valueForKey returning NSNull?)

给出以下代码（使用magicrecord进行coredata获取）：

// Get all of our apps. NSArray * applications = [Application MR_findAllInContext: [NSManagedObjectContext MR_context]]; Application * application = [applications firstObject]; NSLog(@"Test: %@", application.applicationId); NSArray * applicationIds = [applications valueForKey: @"applicationId"]; NSLog(@"Application ids: %@", applicationIds);

我得到以下日志：

Test: 586001240 Application ids: ( "<null>", "<null>" )

我知道applications数组包含两个条目。 每个都有一个唯一的applicationId属性。 我不明白为什么对valueForKey的调用会返回两个空值？ 相反，我应该得到两个NSNumber对象。

我最近发现了关于valueForKey（以前获取唯一条目我会使用枚举并将条目添加到数组中）。 我正在尝试使用valueForKey来提高可读性。 显然我不是正确理解的东西。 关于我哪里出错的提示？

编辑 - 更多详情：

Application类是通过核心数据模型生成的。 界面定义为：

@interface Application : NSManagedObject @property (nonatomic, retain) NSNumber * applicationId; @property (nonatomic, retain) NSString * name; @end

Given the following code (uses magicrecord for the coredata fetching):

// Get all of our apps. NSArray * applications = [Application MR_findAllInContext: [NSManagedObjectContext MR_context]]; Application * application = [applications firstObject]; NSLog(@"Test: %@", application.applicationId); NSArray * applicationIds = [applications valueForKey: @"applicationId"]; NSLog(@"Application ids: %@", applicationIds);

I get the following logs:

Test: 586001240 Application ids: ( "<null>", "<null>" )

I know that the applications array contains two entries. Each has a unique applicationId property. I don't understand why the call to valueForKey is returning me two nulls? Instead I should be getting two NSNumber objects.

I recently found out about valueForKey (previously to get unique entries I would use an enumeration and add the entries to an array). I'm trying to use valueForKey to improve the readability. Obviously I am not understanding something correctly. Any tips on where I am going wrong?

Edit - More details:

The Application class is generated via a core data model. The interface is defined as:

@interface Application : NSManagedObject @property (nonatomic, retain) NSNumber * applicationId; @property (nonatomic, retain) NSString * name; @end

最满意答案

想出来 - 我的问题非常愚蠢。

我不得不改变：

[Application MR_findAllInContext: [NSManagedObjectContext MR_context]];

成为：

[Application MR_findAllInContext: [NSManagedObjectContext MR_defaultContext]];

这解决了这个问题。

Figured it out - Very dumb problem on my end.

I had to change:

[Application MR_findAllInContext: [NSManagedObjectContext MR_context]];

To be:

[Application MR_findAllInContext: [NSManagedObjectContext MR_defaultContext]];

That solved the issue.