yeinsbalaguera / solid

Masterclass SOLID examples

SOLID principles

Open-Closed Principle

In this example you can use the computeArea() method to calculate shape's areas in the client code.

class Client
{
    public static function compute(Figure $figure)
    {
        echo 'The area is ' . $figure->computeArea();
    }
}

You can create a new class for any shape without modifying the related code. For instance, you can create the Circle class and the client should keep working.

class Circle extends Figure
{
    protected float $radio = 0;

    public function __construct(float $radio)
    {
        $this->radio = $radio;
    }

    public function computeArea(): float
    {
        return pi() * pow($this->radio, 2);
    }
}

Liskov Substitution Principle

In this example you can use the printContent() method to calculate shape's areas in the client code. You can also interchange the type by any subtype without affecting the client code.

class Client
{
    public static function printContent(Parser $parser): void
    {
        echo $parser->output();
    }
}

In this case, you can use any parser that extends the main Parser class.

$parser = new Parser([
    [1, 'Steave', 'Developer'],
    [2, 'Andreas', 'Tester'],
]);

// subtype CSV
$csv = new CSVParser([
    [1, 'Steave', 'Developer'],
    [2, 'Andreas', 'Tester'],
]);

// subtype MarkdownTable
$marrkdown = new MarkdownParser([
    [1, 'Steave', 'Developer'],
    [2, 'Andreas', 'Tester'],
]);

Client::printContent($parser);
Client::printContent($csv);
Client::printContent($markdown);