Swift + CoreData：不能在NSManagedObject子类上设置Bool - Bug？

问题描述

我有一个奇怪的问题，我不能看出，我有一个简单的实体与自定义NSManagedObject子类：

  @objc（EntityTest）class EntityTest：NSManagedObject {
 
 @NSManaged var crDate：NSDate 
 @NSManaged var name：String 
 @NSManaged var completed：Bool 
 @NSManaged var completedOn：NSDate 
} 
  

这是问题，我可以创建对象精细并设置所有的值并存储在数组中。然而，后来，当我尝试检索相同的对象，我可以设置所有的值，除了完成字段。我得到一个运行时错误说EXC_BAD_ACCESS，我可以读取值，只是不能设置它。

调试器指向：

  0x32d40ae：je 0x32d4110; objc_msgSend + 108 
 0x32d40b0：movl（％eax），％edx 
  

它被视为一个Objective-C类，并试图发送消息设置布尔值，我知道是有点搞笑CoreData最初表示为NSNumbers。

任何想法？我自己创建了类，不生成。

编辑：

  entity.crDate = NSDate（）//成功
 entity.completed = false //失败
 entity.completed.setValue（false，forKey：completed）//成功
  

所以为了设置bool，使用NSManagedObject的setValue工作而不是直接的setters，

更新：

检查这一点，看起来像第一次我从NSEntityDescription获取后设置值，它使用普通的Swift访问器方法。后来当我尝试访问同一个对象（它存储在一个数组），它试图将其视为一个Objective-C风格对象，并发送一个名为setCompleted的方法的消息。我想这是有道理的，因为我使用点符号来访问它，我使用的@objc指令。

我通过创建一个setCompleted方法，该方法我使用completed = newValue设置值，这使得递归调用回到setCompleted导致它崩溃...奇怪，所以在这一刻仍然不能没有正确的修复。它似乎只发生在Bools。

只有解决方法是使用NSManagedObject的setValueForKey方法。

解决方案

如果您允许 Xcode 6 Beta 3 创建Swift文件，它将创建 CoreData 的 NSNumber 属性布尔 type。

不过，您可以使用Bool作为Swift类型，而不是NSNumber，虽然不使用点语法。
它将用 NSNumber 设置Swift Bool ，这可能会导致点语法中的错误。

---

为了使它显式，你应该使用 NSNumber 对于具有 Boolean 类型的实体中的属性。然后创建一个计算属性（在iBook中使用Swift编程语言在语言指南 - >属性 - >计算属性），返回一个Swift Bool 。所以不会真正存储 Bool 。

像这样：

  @NSManaged var snack：NSNumber 
 var isSnack：Bool {
 get {
 return Bool（snack）
} 
 set {
 snack = NSNumber（bool：newValue）
} 
} 
  

当然，隐藏另一个（NSNumber属性）会很酷，但是要耐心，Apple将来会实现私有属性。

---

编辑：

如果您选中创建skalar类型甚至在自动创建的Swift文件中使用类型 Bool ！

所以我认为这是一个错误。 p>

I have a little strange issue which I can't seem to figure out, I have a simple entity with a custom NSManagedObject subclass:

@objc(EntityTest) class EntityTest: NSManagedObject {

    @NSManaged var crDate: NSDate
    @NSManaged var name: String
    @NSManaged var completed: Bool
    @NSManaged var completedOn: NSDate
}

This is the problem, I can create the object fine and set the all the values and store in in an array. However late on, when I try to retrieve the same object, I can set all the values EXCEPT the "completed" field. I get a run-time error saying "EXC_BAD_ACCESS", I can read the value, just can not set it.

The debugger points to:

0x32d40ae:  je     0x32d4110                 ; objc_msgSend + 108
0x32d40b0:  movl   (%eax), %edx

Maybe some issues due to it being treated as an Objective-C class and trying to send a message to set boolean which I know is a bit funny with CoreData originally representing them as NSNumbers.

Any ideas? I created the class myself, it is not generated.

EDIT:

entity.crDate = NSDate() // succeeds
entity.completed = false // fails
entity.completed.setValue(false, forKey: "completed") //succeeds

So for setting the bool, using the setValue of NSManagedObject works but not the direct setters, though for the non-bool properties, I can set it using the setters.

UPDATE:

While checking this a bit more, it seems like the first time I set the value after getting from NSEntityDescription, it uses normal Swift accessor methods. Later on when I try to access the same object (which was stored in an array) it attempts to treat it as a Objective-C style object and sends a message for method named "setCompleted". I guess it makes sense since I use the dot notation to access it and I used the @objc directive.

I tested this by creating a "setCompleted" method, however in the method I set the value using "completed = newValue" which makes a recursive call back to "setCompleted" causing it to crash... Strange, so at this moment still can't don't have a proper fix. It seems to only happen with Bools.

Only workaround is use the "setValueForKey" method of NSManagedObject. Perhaps file this as a bug report?

解决方案

If you let Xcode 6 Beta 3 create the Swift files for your entities, it will create NSNumber properties for CoreDatas Boolean type.

You can however just use Bool as a Swift type instead of NSNumber, that worked for me without using the dot syntax though.It will set the Swift Bool with a NSNumber, that maybe leads to a bug in the dot syntax.

---

To make it explicit you should use the type NSNumber for attributes in the entity with the Boolean type. Then create a computed property (in iBook The Swift programming language under Language Guide -> Properties -> Computed Properties) to return you a Swift Bool. So would never really store a Bool.

Like so:

@NSManaged var snack: NSNumber
var isSnack: Bool {
    get {
        return Bool(snack)
    }
    set {
        snack = NSNumber(bool: newValue)
    }
}

Of course it would be cool to hide the other (NSNumber attribute), but be patient and Apple will implement private attributes in the future.

---

Edit:

If you check the box create skalar types it will even use the type Bool in the automatically created Swift file!

So I think it is a bug.

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