Using Objects and Ranges With Cases in Ruby

Wed, 29 Mar 2017 00:00:00 +0000

Ruby's case statement provides some nice functionality to be used with objects and ranges. I was recently developing a small application in Ruby on Rails using blood test data where I had to check if a certain test item (i.e. HDL Cholesterol) value belonged to a certain range. I did not want to use a bunch of if statements and I actually found a pretty neat way to implement using the Ruby case.

In my application I have a Rails model called Entry which represents a blood test result with a lot of field data such as blood glucose level, blood pressure level, etc. etc. I want to display this data in the view using Bootstrap 3's nice progress bars and I want the progress bar's contextual class to be changed and determined by the range in which this data point sits in.

If we take total cholesterol as an example, a quick Google search indicates that an ideal value would be less than 200 mg/dL, a high value (not good) would be between 200-239 mg/dL, and a very high value (definitely not good) would be above 240 mg/dL.

To implement this, I created a Recommendations module under the /models directory. All classes belonging to this module will have different ranges to represent what I explained above. This is what the model directory tree looks like:

app/models/
├── application_record.rb
├── concerns
├── entry.rb
├── recommendations
│   ├── blood_glucose.rb
│   ├── diastolic_pressure.rb
│   ├── hdl.rb
│   ├── ldl.rb
│   ├── systolic_pressure.rb
│   └── total_cholesterol.rb
└── user.rb

bootstrap on Andrés Álvarez

Using Objects and Ranges With Cases in Ruby