Software design principles: DRY

Today we'll be exploring a design principle called DRY it 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, with the upcoming of component-based frameworks, we see less and less of reused codes.

DRY Examples

I'm going to demonstrate some simple use-cases, but they should give you a good understanding of what DRY means.

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? Well, think of this code as a little bit more complicated, a full sorting function, and all of a sudden the sorting key changes, you now have to make changes twice, instead of doing it once.

Another good example is validations; this is were 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 in case that exception might ever change.

<?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.

Looking forward to hearing what kind of things you do that you could optimize?

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