瞬态可选NSSet崩溃，出现EXC_BAD_ACCESS错误

I have a transient optional attribute addedImages in Swift as part of an one-to-many relationship within a managed object with the attribute and the accessor methods:

我在Swift中有一个瞬态可选属性addedImages,作为托管对象中具有属性和访问器方法的一对多关系的一部分:

…
@NSManaged public var addedImages: NSSet?
…
@objc(addAddedImagesObject:)
@NSManaged public func addToAddedImages(_ value: MMImage)

@objc(removeAddedImagesObject:)
@NSManaged public func removeFromAddedImages(_ value: MMImage)

@objc(addAddedImages:)
@NSManaged public func addToAddedImages(_ values: NSSet)

@objc(removeAddedImages:)
@NSManaged public func removeFromAddedImages(_ values: NSSet)
…

The failing code is run within a serial queue and crashes with an EXC_BAD_ACCESS error.

失败的代码在串行队列中运行,并因EXC_BAD_ACCESS错误而崩溃。

let backgroundContext = NSManagedObjectContext(concurrencyType: NSManagedObjectContextConcurrencyType.privateQueueConcurrencyType)
backgroundContext.performAndWait {
  print("\(self.addedImages?.count ?? 0) added images")
  self.addToAddedImages(image)
}

It works without issues when I rather define addedImages as non-transient. I'm not sure if this is a normal behavior, and how I could fix this. Thank you for your help.

当我将addImages定义为非瞬态时,它没有问题。我不确定这是否是正常行为,以及我如何解决这个问题。谢谢您的帮助。

1 个解决方案

#1

My assumption that a transient attribute would be initialized with nil during the creation and fetch was wrong. When I tried to access count, the object was simply not in memory. I had to add this to awakeFromFetch and awakeFromInsert, which works.

我假设在创建和获取期间使用nil初始化transient属性是错误的。当我试图访问count时,对象根本就不在内存中。我不得不将它添加到awakeFromFetch和awakeFromInsert,它可以工作。

if self.addedImages == nil {
  self.addedImages = nil
}