smoothphp/querybus

A simple bus for queries

Query Bus

![Software License][ico-license] ![Coverage Status][ico-scrutinizer] ![Total Downloads][ico-downloads], _(*1)

Install

Via Composer, _(*2)

``` bash $ composer require smoothphp/querybus, <sub>(*3)</sub>

## Usage
The query bus exists to execute queries within the domain of the application. Typically these are read only commands, with write operations being performed using the [Command Bus](https://github.com/SmoothPhp/CommandBus).  

The QueryBus is a simple concept, and leaves the majority of the implementation decisions to the developer. A simple implementation is provided for Laravel users.

The query bus exists of 3 components.

* Query  
  The DTO containing the intent and parameters for the query.
* Query Bus  
  Takes a query object, resolves the query handler, and executes it.
* Query Translator  
  Takes a query, and translates to the query handler class name.


### Laravel Users
The Laravel Query bus takes a Query object, and resolves the handler by adding 'Handler' to the class name. This handler class is then resolved by the container and all dependencies are injected.  

For example, `App\Queries\FindUserById` is resolved to `App\Queries\FindUserByIdHandler`, and the `handle` method is executed.  
You are free to implement query handler resolution however you like, though.

#### Service Provider
```php
<?php

return [
    // ...

    'providers' => [
        // ...
        SmoothPhp\QueryBus\Laravel\LaravelQueryBusServiceProvider::class,
    ],
];

Query

<?php

class FindUserById {
    public $id;
    public function __construct(string $id) {
        $this->id = $id;
    }
}

Query Handler

<?php

class FindUserByIdHandler {
    private $client;

    public function __construct(DBClient $client) {
        $this->client = $client;
    }

    public function handle(FindUserById $query) {
        return $this->client->table('users')->where('id', $query->id)->get();
    }
}

Using

<?php

class ExampleController extends Controller {
    private $bus;

    public function __construct(\SmoothPhp\QueryBus\QueryBus $queryBus) {
        $this->bus = $queryBus;
    }

    public function showUser(string $userId) {
        return view('users.show')->with('user', $this->bus->query(new FindUserById($userId)));
    }
}

Change log

Please see CHANGELOG for more information what has changed recently., <sub>(*4)</sub>

Testing

bash $ composer test, <sub>(*5)</sub>

Contributing

Please see CONTRIBUTING and CONDUCT for details., <sub>(*6)</sub>

Security

If you discover any security related issues, please email simon@smoothphp.com instead of using the issue tracker., <sub>(*7)</sub>

Credits

• Simon Bennett
• All Contributors

License

The MIT License (MIT). Please see License File for more information., <sub>(*8)</sub>