The Observer Design Pattern

An explanation of the Observer design pattern and its purpose.

Correction:
Robert Llewellyn and I follow the rule that the PREPERATION of a video not take longer than an hour, not that the video itself take an hour.

http://www.google.ca/search?&q=%22observer+pattern%22

Category:

Howto & Style

Tags:

• software
• engineering
• codingkriggs
• design
• patterns
• subject
• observer
• publisher
• subscriber
• gof
• gang
• of
• four

[zck7]

I've used this pattern for years and years. I and others always just called it the event-callback model, but I guess in order to sell Design Pattern books the design pattern people had to invent an unnecessary new name for it.

[codingkriggs]

@zck7 No conspiracy. :) The GoF tried to choose the best name, sometimes creating a new one if none of the existing ones satisfied them. They also list alternate names. In the case of Observer, they list "Subject Observer, Publish Subscribe, Callback". The GoF made no claim of inventing any pattern or even the idea of patterns themselves. They just normalized our vocabulary as software developers. That is the source of their success, and why their naming is dominant today.

[ComradeAart]

I love this pattern. Funny enough I figured it out myself at the time I first used it, and I didn't know until now it has a name. Is it standardized? Patterns are easy to define yourself, but this kind of standardization is important for Model Driven Engineering.

Liked this video: clear and simple.

[codingkriggs]

Yep. Straight from the original GoF book.

en [dot] wikipedia [dot] org [slash] wiki [slash] Design_Patterns

[gamccoy]

Your book looks cute but please, read the GoF book instead. Failing that, read Code Complete. You sound like you are a serious student and that requires serious references.

Finally, patterns are waaay over hyped.

[codingkriggs]

Thank you for the comment. I own both those books. The GoF book has only one edition which is showing its age, which is why other authors have written books to supplement the GoF book. Code Complete is not my cup of tea, though I have utmost respect for McConnell for a book he wrote on project management called Rapid Development. As for patterns being overhyped, I think most people can agree to that, though how overhyped is probably subject to opinion.

[ArabfilmsArabseries]

...use a UML editor for a change, instead of writing on a napkin.

[neoflyboy]

well, I just was coding software for the last 22 years, have seen a couple of explanations across the times, GoF, O'Reilly HFP, and I think your explanation is very nice.

To make your presentation even better, there are some software tools like techsmith camtasia studio, which allows you to record the screen when you are showing a PPT presentation, and easily add your webcam into one corner. So people can see your UML's, hear your voice and see your face expressiveness.

Thanks for sharing

[TheBlueBear1337]

great idea but you cant use postits...

[angelwhite]

A little bit of code would have made this a lot more tangible. I found I was zoning out about halfway through. I think a few snippets of code would have given me the visual anchors to follow along with you (I learn visually).

[slier81]

pls use some sort of uml design tool

[abinandanagmail]

Nice simple explanation... Many thanks to you.. Gives soo much in a little time...

[shoaibchh]

i got each and everything thanks by the way......

[babapua]

@ArabfilmsArabseries this video is done as simple as possible but not simpler - what's your problem with that my friend?