Movie rental refactor challenge

I got this refactor challenge for a simple ruby script that has 3 objects and produces a statement. In effect we have a Movie object, a Rental object and a Customer object. The purpose of the script is to print out a statement with the customer’s name, order, amount due and frequent renter points.

The code that I received for refactoring has syntax and other errors, which after a quick email exchange I found out where put there intentionally. So it’s more of a fix the code challenge rather than a refactor job, but I did both. Underneath you’ll see the snippets of the code I got:

And the problem object

At first glance we can see that we are dealing with a renting operation in which a customer chooses one or more movies to rent and gets billed accordingly.

We can see from a glance that the customer class is pretty much a mess. We have an unnecessary variable (x = 7) , we have bad variable and method names “add_rental_object_to_list(arg)” , an improper constant call “Movie.NEW_RELEASE” , a couple of typos and worst still:


Now, let’s move on to how I made the code, and look under the hood a bit

Now you must be wondering ‘what happened to all the code logic from the customer class?’

Well I extracted out all that business logic and placed it all inside an Interactor. I did this because all business logic should be extracted and separated from ruby/rails logic. I like to keep my public objects as plain and as dumb as humanly possible. I guess you have heard of the paradigm, ‘slim model fat controller’ or others put it as ‘slim controller fat model’. I for one prefer to keep all my main public objects as slim and as dumb as possible.

I know what you’re thinking, ‘model? controller? what does rails logic have to do with a ruby script?’ and you’d be right. But I am putting out an idea. and as I’ve said it before in a previous post the business logic of your app should be extracted and tested separately. This has many advantages including: a more modular design, easier to read code, easier to extend and maintain, easier to refactor etc.

So first I’ll put the tests


And here is the actual code


I extracted all the logic in this lamba function that you can conveniently call as such:

and it will print out the following:


You can find the code repo here and also other code snippets and scripts.

Have a splendid week!

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