observer-pattern

问题 i was going through a post post about how observer pattern can be implemented in python . on the same post there are these comments. 1) In python you may as well just use plain functions, the ‘Observer’ class isnt really needed. 2) This is great example of what Java programmers are trying to do once they switch to Python – they feel like Python is missing all that crap and try to “port” it. These comments imply that the observer pattern is not really useful in python and there exists other

问题 I have three separate calls to APIs. When all three calls are complete, I am going to aggregate the data and use it to form a separate model object. I figured I would use property observers to accomplish this but I have no idea how it would be implemented. Any help or guidance would be appreciated. I have created a model object for making the network calls that passes the response data into an escaping closure. This is the function where the data is parsed: func loadLibrary() { // League Data

问题 I am using ContentObserver on contacts. But here my problem is atleast once i have to launch my application other wise i am unable to get notification chages. My code like this ContactsContentObserver cco = new ContactsContentObserver(handler); ContentResolver contentResolver = getContentResolver(); contentResolver.registerContentObserver(RawContacts.CONTENT_URI, true, cco); } private class ContactsContentObserver extends ContentObserver { public ContactsContentObserver(Handler h) { super(h);

问题 I have a fully implemented DAO and all my beans inherit an Entity object. Now, I want to create a client notification system whereby, when a user creates/updates/delete an entity to/from a persistence storage, a notification is automatically sent to the client via email. I have a DAO manager that uses a Factory Pattern to return to me a manager of the DAO based on the entity type. e.g EntityManager manager = EntityManagerFactory.createEntityManager(Product.class); each manager has a create(),

问题 i'm trying to implement a custom version of an Observer pattern in c++. These are my classes (just interface): class Observer{ public: void observe(std::string behaviour, Observable * observable); void stopObserving(std::string behaviour, Observable * observable); virtual void notified(std::string behaviour, Observable * observed); // ... }; class Observable{ public: void notifyBehaviour(std::string behaviour); // ... }; And can be used like this: class A : public Observer{ public: void

问题 The Controller class is a singleton, which seems to be a special case allowing for safely passing this to Controller . Netbeans gives Configure "passing suspicious parameters in the constructor" hint for controller.addObserver(this); which makes me ask what the better technique would be, although I gather it's not a good approach. package net.bounceme.dur.usenet.swing; import java.util.Observable; import java.util.Observer; import java.util.logging.Logger; import javax.mail.Folder; import

问题 I'm building an application which contains a GUI and a Model. I'm using the Observer pattern (using java's built in interfaces) to update the GUI when fields in the model are changed. This is generally working fine, but I have a situation in which a particular String variable in the model (specifically the url of a file) can be changed by two separate JTextFields (swing) the contents of which actually reflects the value of the model variable in question. The issue I am having comes from the

问题 Recently I got into implementing a message dispatching system that uses the "Observer pattern": nothing special here. As I developed it I thought it would be nice to send "Message" objects from the "subject" that could be fundamentally different from each other and could be read from the many "observers". These different messages took the form of different message classes (for example, think about the "User Logout message", "Screen mode toogle" and "Volume level changed", all of these need

问题 I have an activity which needs to perform an operation once a connection to a network has been established. I tried implementing the Observer pattern but am getting a NullPointerException when I try to register the Observer activity to the subject. Any thoughts? NetworkStatus public class NetworkStatus implements NetworkStatusSubject, Runnable { List<NetworkObserver> observerList; Context context; public NetworkStatus(Context context) { this.context = context; } public static boolean

问题 I'm using AVPlayer's -addBoundaryTimeOserverForTimes:queue:usingBlock: to execute some code at a specific time in my video (in this case, I want a un-hide a button when my video reaches its duration. Code is as follows: - (void)viewWillAppear:(BOOL)animated { ... _player = [AVPlayer playerWithURL:videoURL]; AVPlayerLayer *newPlayerLayer = [AVPlayerLayer playerLayerWithPlayer:_player]; [newPlayerLayer setFrame:_videoView.bounds]; [_videoView.layer addSublayer:newPlayerLayer]; _observer = [