observer-pattern

问题 I want to call a method before the execution of every and each controller's method. I don't want to go and call the method in every method. I just want to call it from one place and it will be called before any method of any controller in magento. And I am sure we can do this but I don't know how it can be accomplished. Please provide your suggestions. Hope we can resolve this or may some expert guys already resolved this. Thanks. 回答1: You need to create an Observer that binds to the

问题 In my application I have many classes. Most of these classes store quite some data, and it is important that other modules in my application are also 'updated' if the content of one of the data classes changes. The typical way to do this is like this: void MyDataClass::setMember(double d) { m_member = d; notifyAllObservers(); } This is a quite good method if the member is not often changed and the 'observing classes' need to be up-to-date as fast as possible. Another way of observing the

问题 I have an issue with Observable in Angular 2. I subscribe my component to an observable, then when my service has new value, my component is notified. Problem is when the observer push an error, like an HTTP error, my observable is closed, so my component is no more notified. Question How can I do to make my component continue listening my service even when I have an error ? Example Here an example Here my code : Component constructor(private appService: AppService) { //I subscribe my

问题 I have a dropdown box in my GUI which shows the contents of an ArrayList in another class. New objects can be added to the ArrayList elsewhere in the GUI, so I need to know when it is updated, so I can refresh the dropdown menu. From what I can gather, my two options are to extend the ArrayList class to allow me to add my own changeListener to it, or to make the class which contains the ArrayList in question extend observable. Which would be a more appropriate solution? 回答1: The two solutions

问题 Is Eventbus more a Mediator or an Observer? According to Google, "eventbus mediator" gets 2.430 hits and "eventbus observer" gets 3.850 hits. From the description, they would both match what I was trying to do (the mediator even a little more). So does eventbus implement a specific pattern or is it up to me which I say it is? 回答1: Often, a given piece of code isn't intrinsically an example of one pattern or another. This is why they're called "patterns" (rather than, say, "implementation

问题 trying to find an example of this, it's possible that I am not going the right way around it, or that my mind has over simplified the concept of the observer pattern. I want to create a class that controls messages from a web service, and I want this class to monitor the changes of many other operations. The observer pattern examples I have seen demonstrate many observers watching a single observable, can I (or should I) do this the other way round? What else should I be doing? 回答1: Just

问题 I have an observable collection and an observer. I want the observer to be a trait implementation of trait Observer . The observable object should be able to notify each observer when some event occurs. This should explain my intentions: struct A { observables: Vec<Observable>, } impl A { fn new() -> A { A { observables: vec![], } } } trait Observer { fn event(&mut self, _: &String); } impl Observer for A { fn event(&mut self, ev: &String) { println!("Got event from observable: {}", ev); } }

问题 The short version of the question: I have a class with a ton of declared properties, and I want to keep track of whether or not there have been any changes to it so that when I call a save method on it, it doesn't write to the database when it isn't needed. How do I update an isDirty property without writing custom setters for all of the declared properties ? The longer version of the question: Let's say that I have a class like this: @interface MyObject : NSObject { @property (nonatomic,

问题 There is a question already answered which is In C#, isn't the observer pattern already implemented using Events? It asks if the observer pattern is already implemented in c# using events. While I get the events and observer pattern, isn't the observer pattern really just delegates and events is a further implementation? 回答1: You are correct. An event is simply a delegate with some slightly different functionality. All of the observer pattern can be implemented with delegates without ever

问题 I'd like to add an Auditor Observer which does an action anytime after_create for 3 models (books, characters, authors)... I recently heard of the Observer capability but can't find any documentation on the ability. Is it support in Rails 3? How do I create an Auditor Observer that does something after_create for 3 models? Thanks 回答1: Rails observers are sweet, You can observe multiple models within a single observer First, you need to generate your observer: rails g observer Auditor Then, in