observer-pattern

问题 I read this and this and found out that in class B I need to save a reference to class A and when something happens in class B we execute a method defined by an interface that class A implements. Well somehow I understood it. I use interfaces in a bit different way to call a callback: interface IHelper { void onActionDone (); void onActionFailed (); } public class Helper implements IHelper { public Helper (Param param) { // here we do what Helper class intended to do // ... // now call the

问题 Is there an observer which can be used to observe events when a product is removed from the cart? I haven't found any. What I have found is checkout_cart_update_items_after which can be used if a product is removed by altering the product count, but not when the user uses the remove button. The only alternative I see in the moment is checkout_cart_save_after which is used whenever the cart changes. Of course this needs custom logic which check which product was removed. Not perfect. So is

问题 I was reading some article to understand a little bit more how AngularJS works. One of the terms that I didn't understand is Dirty Checking . What is it exactly? It seems like the Observer pattern but apparently it's better. Can you help me understand this please? EDIT : it can be also useful for people who wants to learn more about that to watch this video from swiip at NgEurope some years ago. 回答1: From this link: Angular defines a concept of a so called digest cycle. This cycle can be

问题 I am trying to understand observer pattern and stuck at one particular point. In my understanding, once an observer subscribes to notify them on any event change, the subscription is stored somewhere and then when event changes the subscriber is notified. In practical scenarios I should store the values in a database or a file for persistence reasons and inform them once event occurs by getting from db and looping through the list. Is this correct understanding? I do not see any example

问题 I'd like to know what pattern to use, if I need my Service to share it's dynamic data between Controller, Directives, etc. The reason I mention dynamic, is because I'd like to load new data and this data needs to be available in any other Controller, Directive, etc. For example, if a Directive generates a UL LI, it would have to re-generate it if the data inside the Service has changed! I've initially opened the following ( How to create reset() method in Service that return promise? ) and

问题 Why does the Observer interface has Observable o as a parameter? Do you recommend using Javas existing classes (implements Observer; extends Observable)? public class Test implements Observer { void update(Observable o, Object arg); } 回答1: It receives the Observable reference so that the Observer can use it to address the way it will handle the Object arg that was passed. Also, the Observer could call deleteObserver to remove itself once it finished the job. You shouldn't use them. And it's

问题 This question is not in general about the observer pattern. It is focused on the use of decorators in that pattern. The question is based on the answer of a similar question. #!/usr/bin/env python3 class Observable: """ The object that need to be observed. Alternative names are 'Subject'. In the most cases it is a data object. """ def __init__(self): self._observers = [] def register_observer(self, callback): self._observers.append(callback) return callback def _broadcast_observers(self,

问题 I've been looking into ways to show data from my DB in a ListView while keeping track of changes in the database. Let's say I have a chat app that shows a ListView of all the chatrooms I am a member of. the query for the adapter is SELECT * FROM CHAT_ROOM ORDER BY UPTDATE_TIME , meaning I want the chatrooms with recent activity to be shown first. as I am in the ChatroomListActivity a message is received for chatroom number 3, this means it needs to become now chatroom number one and rearrange

问题 I have a System (game) which I try to implement using the architecture Model-View-Presenter. What I have done right now is a while loop in the presenter that calls continuously the view methods for displaying. The way I do this is using a Producer/Consumer pattern, where the View register and event handler for touch events(Android) and produce the corresponding touch imstances, that the presenter consumes in the while loop. Now I would like to use the pattern Observer/Suscriber between The

问题 I'm trying to do this: In my GUI, I have one JTable with a custom model, and in other part of the GUI, I have one panel where i draw some arrows. I want to "synchronize this two view. So let's say if we have 5 rows in my JTable, I will draw 5 arrows in the panel of arrows. If I make a modification in the number of row, I must have the same number of row. So I'm trying to use Design Pattern Observer. To make simple, I try to provide an example computable in one file: I create n buttons in my