I’m surprised how little there is in Rails’ documentation about this. Basically, ActionMailer in Rails 3 introduces the use of Interceptors (called before the message is sent) and Observers (after the message is sent). To set up an Observer, add the following to an initializer: class MailObserver def self.delivered_email(message) # Do whatever you want with … Read more
Command, callback and observer patterns have different semantics: callback – notifies a single caller that some operation finished with some result observer – notifies zero to n interested parties that some event (for example a finished operation) happened command – encapsulates a operation call in an object thus making it transferable over a wire or … Read more
Yes, you can. There are tons of ways to do it. And there is no need to use the “evil” eval function (please yahoogle why it should be avoided) as pointed out here: http://javascript.about.com/library/bleval.htm var tmpFunc = new Function(codeToRun); tmpFunc(); Whether it was JSON at any stage should be irrelevant.
How can I set up my Activity to be listening to the Service? Is this the best way to approach this problem? You have three major options, as I see it: Polling. The Activity periodically asks the Service for the latest data. IMHO, this option sucks, but it’s certainly possible. Callbacks. Per jax’s answer, the … Read more
Rails 3.1 finally comes with API for this: http://api.rubyonrails.org/v3.1.0/classes/ActiveModel/ObserverArray.html#method-i-disable ORM.observers.disable :user_observer # => disables the UserObserver User.observers.disable AuditTrail # => disables the AuditTrail observer for User notifications. # Other models will still notify the AuditTrail observer. ORM.observers.disable :observer_1, :observer_2 # => disables Observer1 and Observer2 for all models. ORM.observers.disable :all # => disables all observers … Read more
https://stackoverflow.com/a/6270150/3675925 You probably want to look into the observer pattern. Here’s some sample code to get you started: import java.util.*; // An interface to be implemented by everyone interested in “Hello” events interface HelloListener { void someoneSaidHello(); } // Someone who says “Hello” class Initiater { private List<HelloListener> listeners = new ArrayList<HelloListener>(); public void addListener(HelloListener … Read more
Publisher-subscriber vs Observer [closed]
According to tell dont ask, push is better – or more OO. You don’t want to query object for data so you can do something, you want object to do it, because he’s the one who knows his data. Related article about evil getters
Quoting directly from the paper: To illustrate the precise problems of the observer pattern, we start with a simple and ubiquitous example: mouse dragging. The following example traces the movements of the mouse during a drag operation in a Path object and displays it on the screen. To keep things simple, we use Scala closures … Read more