注：答案见底部“编辑”。
我正在编写一个自定义的NSObject，它将异步初始化自己，然后在它完成时发送一个NSNotification，以便我可以将它附加到我的UITableView的数据源中。这是课堂：
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“selector”属性尝试了几种不同的方法，但运气很差。
以下是发送通知时的代码：
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
除了“下载完成”。
非常感谢大家的帮助。
编辑：接受的答案指出了问题所在。我只是测试我的代码，而没有在任何地方实现初始化的类。结果，为了保存记忆，ARC用我的朋友对象做了一些事情。出于测试的目的，我把它附加到一个全局数组中，并在应用程序中的任意按钮被按下时打印数组的内容，使ARC认为我在某种程度上使用了它。
最佳答案
您的Friend实例可能已被ARC自动释放。你有很强的参考价值吗？
将这些行添加到Friend类中以进行检查：
deinit {
print("\(userID) deallocated")
}
关于swift - 在NSObject中收到NSNotification时的调用方法，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/49225278/