Tag Archives: observer

Keep it Simple, Stupid!

Keep it Simple, Stupid!A while back I wrote a blog post on coupling and the observer pattern. Looking back, I did a pretty poor job describing what it wrong about it. I will attempt to correct this.

We all want simple and descriptive code. Code that is self documented. Code that makes sense, Code that tells us a story. Lets look at a kind of code I have seen many times, in many different variations, using observer based asynchronous javascript code:

 
var ListView = {
  init: function() {
    this.feed.onItemsReady(this.onFeedItemsReady);
  },
  onFeedItemsReady: function(items){
    // do something
  }
  // ...
}

At first, this looks descriptive, and it is, kinda. It’s an object describing the implementation of a publisher it is observing.
That doesn’t sound right. It is telling us about the implementation details and why it is doing things rather than what this object is responsible for and what it is doing. We already know all that!
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PubSub / Observer Pattern and Coupling

PubSub (or the observer pattern) is obviously the hottest pattern in client side development, and I would like to take a shot at trying to refine the best practices for using it in a flexible and robust way.

The definition provided in the original Gang of Four book on Design Patterns states:

“Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically”

As in any design pattern, an important part is to keep the application loosely coupled and with high cohesion.
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