Software design principles: DRY

Today we’ll be exploring a design principle called DRY which stands for Don't Repeat Yourself. Of course, a pretty obvious one, meaning you shouldn’t type code more than once.

The principle states: “Every piece of logic must have a single unambiguous representation within a system”.

Of course, we see fewer and fewer reused codes with the upcoming component-based frameworks.

DRY Examples permalink

I will demonstrate some simple use cases, but they should give you a good understanding of DRY.

const foods = ['🧀', '🌶', '🍉'];
const animals = ['🦞', '🐁', '🐕'];

revFoods = foods.reverse();
revAnimals = animals.reverse();

This is only a very simple function, but this can be converted to a DRY part:

const foods = ['🧀', '🌶', '🍉'];
const animals = ['🦞', '🐁', '🐕'];

let reverse = (input) => {
  return input.reverse();
};

revFoods = reverse(foods);
revAnimals = reverse(animals);

Why would you do this? Think of this code as a bit more complicated, a full sorting function, and suddenly, the sorting key changes. You now have to make changes twice instead of doing it once.

Another good example is validations; this is where I personally fail sometimes.

<?php
class Validator {
    public function validate(array $post)
    {
        if(!isset($post['title']) {
            throw new \Exception('validation failed, no title set');
        }
        if(!isset($post['date']) {
            throw new \Exception('validation failed, no date set');
        }
        if(!isset($post['description']) {
            throw new \Exception('validation failed, no description set');
        }
    }
}

While it’s not specifically a violation, we could enhance this and make our lives easier if that exception ever changes.

<?php
class Validator {

    private $validateAttributes = [
        'title',
        'date',
        'description'
    ];

    public function validate(array $post)
    {
        foreach ($this->validateAttributes as $attribute) {
        if (!isset($post[$attribute])) {
            throw new \Exception('validation failed, no '.$attribute.' set');
        }
    }
    }
}

There you go. I hope you learned something about not repeating yourself in code.

I am looking forward to hearing what things you do that you could optimize.

Thank you for reading, and let’s connect! permalink

Thank you for reading my blog. Feel free to subscribe to my email newsletter and connect on Facebook or Twitter