Design patterns: Simple factory

Artur Lasota — Thu, 27 Jun 2019 12:04:23 +0000

The simple factory is one of the creational design patterns. It creates objects with the same interface. The concrete object is created depend on arguments in the method.

Example:

Let assume that we like to have different configs for an application depend on the environment. So we create two classes:

class ConfigProd implements ConfigInterface
{
    public function getDatabaseName(): string
    {
        return 'database_prod';
    }
}

class ConfigDev implements ConfigInterface
{
    public function getDatabaseName(): string
    {
        return 'database_dev';
    }
}

Each class implements the same interface:

interface ConfigInterface
{
    public function getDatabaseName(): string;
}

And of course we have a simple factory:

class ConfigFactory
{
    public function createConfig(string $environment): ConfigInterface
    {
        switch ($environment) {
            case 'dev':
                return new ConfigDev();
            case 'prod':
                return new ConfigProd();
        }
    }
}

If we need production configuration then we pass string prod to factory method and we get production configuration. This same for develop environment.

$configProd = (new ConfigFactory())->createConfig('prod');
$configDev = (new ConfigFactory())->createConfig('dev');

So it's all.

Logic in the factory can be more complicated but we don't need to worry about this. We only take configuration where we need it.

P.S.
It's hard to find a good example. If you have good let me know in comments. Thanks.

Source:
https://medium.com/nestedif/java-simple-factory-pattern-9c2538dd0265

Source code:
https://github.com/lasotaartur/design-patterns/tree/master/Creational/SimplyFactory

DEV Community: Artur Lasota

Design patterns: Simple factory

Example: