swift - 在 NSObject 中接收到 NSNotification 时调用方法

Question

注意:请参阅底部的“编辑”以获得答案。

我正在编写一个自定义的 NSObject，它会异步初始化自己，然后在它完成时发送一个 NSNotification，这样我就可以将它附加到我的数据源中UITableView。这是类(class):

class Friend: NSObject {
var userID: String!
var schedule: Schedule!

init(friendUserID: String) {
    super.init()
    print("Initializing Friend.")
    self.userID = friendUserID
    let notificationIdentifier = friendUserID + "hasFinishedDownloading"
    print("Adding observer for:", notificationIdentifier)
    nc.addObserver(self, selector: #selector(haveFinishedDownload), name: Notification.Name(notificationIdentifier), object: nil)
    let friendSchedule = Schedule(userID: friendUserID)
    self.schedule = friendSchedule
}

@objc func haveFinishedDownload(notification: Notification) {
    print("Download Finished.")
    print(notification)
} 
}

在添加观察者时，我为“选择器”属性尝试了几种不同的方法，但运气不佳。

发送通知时的代码如下:

class Schedule: NSObject {

//The Key is what day it meets period 4
//The value is an SSAClass object
var ssaClassesDictionary:Dictionary<Int, SSAClass> = [:]

func addClassToDicitonary(classObject: SSAClass!) {
    self.ssaClassesDictionary[classObject.day!] = classObject
}

func fillClasses(userID: String!) {
    print("Filling Classses")
    var userOrTeacher: String!

    switch isUserTeacher(user: userID) {
    case true:
        userOrTeacher = "Teachers"
    case false:
        userOrTeacher = "Users"
    }
    print("Ref about to run")
    ref.child(userOrTeacher).child(userID!).child("c").observe(.value, with: {(snapshot) in
        print("Ref has started downloading")

        if (snapshot.value != nil) {
            let snapshotValue: [String] = snapshot.value as! [String]
            print("snapshot.value != nil")
            var numberDownloaded = 0

            for i in snapshotValue {
                print("running for loop iteration:", i)
                ref.child("Classes").child(i).observeSingleEvent(of: .value, with: {(snapshot) in

                    let value = snapshot.value as! Dictionary<String, Any>

                    //"year", "1", "2", or "3"
                    var customTerm: String!

                    //"year", 1, 2, or 3
                    let term = value["term"]
                    switch term {
                    case is String.Type:
                        customTerm = "year"
                    case is Int.Type:
                        customTerm = "\(term!)"
                    default: customTerm = "year"
                    }

                    let ssaClass = SSAClass(classID: i, AB: value["AB"] as! Bool, Sci: value["Sci"] as! Bool, name: value["n"] as! String, room: value["room"] as! String, term: customTerm, day: value["d"] as! Int)
                    if ssaClass.term == "year" || ssaClass.term == "3" {
                        self.addClassToDicitonary(classObject: ssaClass)
                    }

                    numberDownloaded = numberDownloaded + 1
                })
            }

            DispatchQueue.global(qos: .background).async {
                //This is run on the background queue
                print("Running asynchronous Code")
                while numberDownloaded < snapshotValue.count {
                }

                DispatchQueue.main.async {
                    print("Finished While Loop, going back to main thread")
                    //This is run on the main queue, after the previous code in outer block
                    //Post notification
                    let notificationIdentifier = userID + "hasFinishedDownloading"
                    print("Posting Notification for:", notificationIdentifier)
                    nc.post(name: Notification.Name(notificationIdentifier), object: nil)
                }
            }

        }

    })
}


init(userID: String!) {
    super.init()
    fillClasses(userID: userID)
}
}

所有打印输出运行:

Initializing Friend.
Adding observer for: 19wangdhasFinishedDownloading
Filling Classses
Ref about to run
Default
Ref has started downloading
snapshot.value != nil
running for loop iteration: CH402 - 1
running for loop iteration: CH404 - 1
running for loop iteration: CH406 - 2
running for loop iteration: CS400 - 11
running for loop iteration: CS411 - 11
running for loop iteration: EN301 - 3
running for loop iteration: EN302 - 1
running for loop iteration: EN4014 - 2
running for loop iteration: FR360 - 1
running for loop iteration: HI300 - 8
running for loop iteration: MA405 - 2
running for loop iteration: MA406 - 1
running for loop iteration: MA501 - 2
running for loop iteration: MA506 - 1
Running asynchronous Code
Finished While Loop, going back to main thread
Posting Notification for: 19wangdhasFinishedDownloading

“下载完成”除外。

非常感谢所有帮助。

编辑:接受的答案指出了问题。我只是在测试我的代码，而没有在任何地方实际实现初始化的类。结果，ARC对我的 Friend 对象进行处理以保留内存。出于测试目的，我通过将它附加到全局数组并在按下我的应用程序中的随机按钮时打印数组的内容来修复它，让 ARC 认为我以某种方式使用它。

Answer 1

您的 Friend 实例可能已被 ARC 自动释放。你有强烈的引用吗？

将这些行添加到您的 Friend 类中以检查它:

deinit {
    print("\(userID) deallocated")
}