Managing Dependencies with POODR

I recently spent some time preparing a talk on Managing Dependendencie, a topic cover in the POODR book by Sandi Metz.

Programming is great:

I came from  a sales position where the only keeping me there was the paycheck. I am person that enjoys perpetual learning and not that sales can't be a perpetual end to learning it can also be a drain. I now have the ability to now make things that matter and be a part of something rather than just sell the idea of it. I now have the privilege of maintaining an application with a lot of legacy code.

In sales I have learned to observe the situation and I have notice that programmers are notorious for knocking the previous developer. Rather than understand the code they choose to curse the code for its brittleness and unending work to update with change.

Dependencies:

A recurring misstep in the code I see is the problem I see in my work code but as well in other is change is hard to work due to the large amount of dependencies in the code. Dependencies are the messages sent between objects. In the example below, there is a message being received in the initializer and an outgoing message in the :gear_inches method.

*Please note that the attributes are incoming messages, chain-rig, cog, rim, and tire.

Problems:

The problem with dependencies is that there are too many. The idea of creating Practical Object Oriented Design is to have the least amount of dependencies.

Solution:

Writing maintainable code is another goal having a practical design. As a programmer you should be able to revisit your code and easily understand what is going and also easily implement a new change. In the above examples, the Gear is too dependent on knowing about the Wheel and how its made and which order the rim and tire should be placed in the argument.

The suggestion is to instead pass in the wheel as an argument; this free up the ability for the gear to depend less on the Wheel but also allow other parts of the bicycle without getting the way of the Gear and Wheel relationship.

I hope this post has been useful and also hope to share more info on the subject in future post. *Examples came from the book Practical Object Oriented Design in Ruby, I highly recommend this book to all new and experienced Rubyist.