NSManagedObject在Swift中实现协议时发生EXC_BAD_ACCESS错误 [英] EXC_BAD_ACCESS error for NSManagedObject implementing a protocol in Swift

问题描述

我有以下两种方法：

func isAuthenticated() -> Bool {
    var currentUser: CurrentUser? = self.getCurrentUser()

    if currentUser == nil {
        return false
    }

    self.token = getUserToken(currentUser!.username)
    if self.token == nil {
        return false
    }

    if !tokenIsValidForUser(self.token!, user: currentUser!) {
        return false
    }

    return true
}

func tokenIsValidForUser(token: AuthenticationToken, user: UserObject) -> Bool {
    if token.username != user.username {
        return false
    }

    return true
}

当我调用 isAuthenticated（）时， c $ c> tokenIsValidForUser（）与 EXC_BAD_ACCESS ，显然在CurrentUser对象上。

When I call isAuthenticated(), it fails on the first line of tokenIsValidForUser() with EXC_BAD_ACCESS, apparently on the CurrentUser object.

我的理解是，当对象不再存在时，你会得到这种错误，但我不能理解为什么会是这种情况。

My understanding si that you get this kind of error when the object no longer exists, but I cannot understand why this would be the case.

对象类型CurrentUser被声明as：

The object type CurrentUser is declared as:

protocol UserObject {
    var username: String { get set }
}

class CurrentUser: NSManagedObject, UserObject {

    @NSManaged var username: String

}

推荐答案

我在这里找到了这个问题的解决方案：

I found the solution to this issue here:

http://lesstroud.com/dynamic-dispatch-with-nsmanaged-in-swift/

本质上，当在NSManaged对象上实现协议时，这是Swift的一个奇怪。我不得不在CurrentUser类中的@NSManaged属性中添加 dynamic 关键字，以使类看起来像这样：

Essentially, this is a quirk of Swift when implementing protocols on Objects that are NSManaged. I had to add the dynamic keyword to my @NSManaged properties in the CurrentUser class, so that the class looked like this:

class CurrentUser: NSManagedObject, UserObject {

    @NSManaged dynamic var username: String

}

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