在使用@escaping闭包时创建可观察对象的问题

Question

我正在尝试为NSManagedObjectContext save()操作编写一个可观察对象，但没有成功。该函数既不会触发onNext事件，也不会触发onCompleted事件，因此会立即被释放。当我调试断点时，它显示Disposables.create()和@escaping通知闭包在不同的线程上工作。请告诉我在下面的代码中我做错了什么，并帮助解决问题。

func save() -> Observable<Void> {
    guard base.hasChanges else { return Observable.just(()) }
    return Observable.create { observer -> Disposable in
        var token: NSObjectProtocol?
        token = NotificationCenter.default.addObserver(forName: .NSManagedObjectContextObjectsDidChange, object: self, queue: nil) { _ in
            observer.onNext(()) /* Is executed on the other thread and is never called */
            observer.onCompleted()
            NotificationCenter.default.removeObserver(token!)
        }
        
        base.perform {
            do {
                try base.save()
            } catch {
                observer.onError(Error.some)
            }
        }
        return Disposables.create() \* Immediately calls this func *\
    }
}

Answer 1

func save() -> Observable<Void> {
    guard base.hasChanges else { return Observable.just(()) }
    return Observable.create { observer -> Disposable in
        let queue = DispatchQueue(label: "Save")
        queue.sync {
            self.base.perform {
                do {
                    try self.base.save()
                    observer.onNext(())
                    observer.onCompleted()
                } catch {
                    observer.onError(NSManagedObjectContext.ReactiveError.save)
                }
            }                
        }
        return Disposables.create()
    }
}

Answer 2

在我看来，这应该是可行的：

func save() -> Observable<Void> {
    Observable.create { observer in
        base.perform {
            do {
                try base.save()
                observer.onNext(())
                observer.onCompleted()
            }
            catch {
                observer.onError(error)
            }
        }
        return Disposables.create()
    }
}