Generic Services

Introduction

Pionia Generic Services get their inspiration from Django Rest Framework’s Generic Views. They provide a set of actions that are common in most CRUD applications. This is to help you focus on the complex business logic and not the repetitive CRUD work. But it is not just CRUD, you can query random and paginated data too. You can also add your own actions as you see fit. This feature is available starting from the core version of v1.1.2.

The Mixins#

There a few mixins that have been provided to help you with the CRUD operations. These mixins are:

CreateMixin#

This mixin adds the create action to whatever generic service you have added. It is used to create a new record in the database. You can specify the columns to create in the table by providing the $createColumns array property in the service.

DeleteMixin#

This mixin adds the delete action to whatever generic service you have added. It is used to delete a record from the database by pk_field defined in the service.

ListMixin#

This mixin adds the list action to whatever generic service you have added. It also detects if the request is paginated and applies the pagination to the data accordingly. You can customise the columns to return by defining the $listColumns array property in the service.

RetrieveMixin#

This mixins adds two actions which actually perform the same operation. The retrieve and the details action. They are used to get a single record from the database by the pk_field defined in the service. If the $listColumns property is defined, it will return only those columns.

RandomMixin#

This mixin adds the random action to whatever generic service you have added. The number of records returned is by default 1. But this can be overridden by defining the size or limit parameter in the request. If the size is finally one, it will return an object otherwise an array of objects.

UpdateMixin#

This mixin adds the update action to whatever generic service you have added. It is used to update a record in the database. You can specify the columns to update in the table by providing the $updateColumns array property in the service. If these are not defined, then all/only the table columns that are defined in the request will be updated(partial update). Also, the item to update will depend on the pk_field defined in the service. By default this is id.

The GenericService#

This is the core class that provides the basis for all the actions. It is a class that extends the BaseRestService class so you no longer need to do that. All available methods can be found here in the api reference.

You don’t need to interact with this class directly but through the following generic services.

1. RetrieveCreateUpdateService
2. RetrieveListCreateService
3. RetrieveListCreateUpdateDeleteService
4. RetrieveListDeleteService
5. RetrieveListRandomService
6. RetrieveListUpdateDeleteService
7. RetrieveListUpdateService
8. UniversalGenericService

Creating you custom generic service can be done as follows:

use Pionia\Generics\Base\GenericService;

class CreateRandomService extends GenericService
{
    use CreateMixin, RandomMixin;
}

Now you can let you services extend this class and you will have the create and random actions available.

use application\services\CreateRandomService;

class MyService extends CreateRandomService
{
    public string $table = 'users';

    public array $createColumns = ['name', 'age', 'gender']
}

Remember you still need to register all these service as usual. In your request you can now call the create and random actions.

{
  "SERVICE": "create_random",
  "ACTION": "random",
  "size": 3
}

The above request will return 3 random records from the users table.

RetrieveCreateUpdateService#

This generic service provides the retrieve, create and update actions.

use Pionia\Generics\Base\RetrieveCreateUpdateService;

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';
    public array $createColumns = [];
}

RetrieveListCreateService#

This generic service provides the retrieve, list and create actions.

use Pionia\Generics\Base\RetrieveListCreateService;

class StudentService extends RetrieveListCreateService
{
    public string $table = 'students';
    public array $createColumns = [];
}

RetrieveListCreateUpdateDeleteService#

This generic service provides the retrieve, list, create, update and delete actions.

use Pionia\Generics\Base\RetrieveListCreateUpdateDeleteService;

class StudentService extends RetrieveListCreateUpdateDeleteService
{
    public string $table = 'students';
    public array $createColumns = [];
    public ?array $updateColumns = null;
}

RetrieveListDeleteService#

This generic service provides the retrieve, list and delete actions.

use Pionia\Generics\Base\RetrieveListDeleteService;

class StudentService extends RetrieveListDeleteService
{
    public string $table = 'students';
}

RetrieveListRandomService#

This generic service provides the retrieve, list and random actions.

use Pionia\Generics\Base\RetrieveListRandomService;

class StudentService extends RetrieveListRandomService
{
    public string $table = 'students';
}

RetrieveListUpdateDeleteService#

This generic service provides the retrieve, list, update and delete actions.

use Pionia\Generics\Base\RetrieveListUpdateDeleteService;

class StudentService extends RetrieveListUpdateDeleteService
{
    public string $table = 'students';
    public ?array $updateColumns = null;
}

RetrieveListUpdateService#

This generic service provides the retrieve, list and update actions.

use Pionia\Generics\Base\RetrieveListUpdateService;

class StudentService extends RetrieveListUpdateService
{
    public string $table = 'students';
    public ?array $updateColumns = null;
}

UniversalGenericService#

This generic service provides all the actions. It is the most generic of all the generic services.

use Pionia\Generics\Base\UniversalGenericService;

class StudentService extends UniversalGenericService
{
    public string $table = 'students';
    public array $createColumns = [];
    public ?array $updateColumns = null;
    public ?array $listColumns = ['id', 'name'];
    public string $pk_field = 'id';
}

Customization#

$table#

This defines for us the table we are going to be interacting with. It is a required option.

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';
}

All the other services will require you to define this. This is the table that the service will be interacting with.

$pk_field#

This defines the primary key field of the table. By default it is id. But you can override it to be any other field.

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';
    public string $pk_field = 'student_id';
}

$createColumns#

This defines the columns that will be created when the create action is called. It is an array of strings.

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';
    public ?array $createColumns = ['name', 'age', 'gender'];
}

Any other columns that are not defined in this array shall be ignored. This is requred for all create services.

$updateColumns#

This defines the columns that will be updated when the update action is called. It is an array of strings.

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';
    public ?array $updateColumns = ['name', 'age', 'gender'];
}

If this is not defined, then all the columns that are defined in the request will be updated. This param is optional.

$listColumns#

This defines the columns that will be returned for all actions that return data back to the end user. It is an array of strings.

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';
    public ?array $listColumns = ['id', 'name'];
}

The above implies that whether we are hitting list, retrieve, random or any other action that returns data, only the id and name columns will be returned. This is optional and defaults to * if not defined.

$limit#

This defines the size of records to return. It is an integer. It will henceforth be replaced by the LIMIT or limit on the request if it is defined or in the PAGINATION or pagination key in the request.

By default, this is set to 10 records.

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';
    public int $limit = 10;
}

$offset#

This defines the offset where to start querying from. It is an integer. It will henceforth to be replaced by the OFFSET or offset on the request if it is defined or in the PAGINATION or pagination key in the request.

By default, this is set to 0 records.

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';
    public int $offset = 0;
}

Overriding Actions#

You can override any of the actions provided by the generic services. This is done by defining the action in the service.

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';

    public function create(): BaseResponse
    {
        // Your custom logic here
        $data = $this->request->getData();

        // perform your own way of creating the record

        return BaseResponse::JsonResponse(0, "your message", $data);
    }
}

The fact that Pionia is structured in an OOP way, you can override any of the actions provided by the generic services. This is just normal PHP OOP inheritance.

Adding Custom Actions#

You can add your own custom actions to the generic services. This is done by defining the action in the service.

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';

    public function customAction(): BaseResponse
    {
        // Your custom logic here
        $data = $this->request->getData();

        // perform your own custom action

        return BaseResponse::JsonResponse(0, "your message", $data);
    }
}

You can now call this action in your request by setting the ACTION key to custom_action.

{
  "SERVICE": "student",
  "ACTION": "custom_action"
}

Overriding getters#

You can also tell the service how to query one item and how to list multiple items. This is can be handy where for example you want to add complex where clauses to your queries.

For this cause, you can override the getItem and getItems methods in service.

class StudentService extends RetrieveCreateUpdateService
{
    public string $table = 'students';

    /**
     * Override this in your service to define the basis to return single item details
     * @return null|object
     */
    public function getItem(): ?object
    {
        return null;
    }

    /**
     * Override this in your service to define the basis to return multiple items from the database
     * @return null|object
     */
    public function getItems(): ?array
    {
        return null;
    }
}

Generic Services Signals(Hooks)#

Generic Services come baked with hooks that enable you to run custom code before or after the CRUD operations. The following are some of these hooks:

preCreate#

This hook is called before the create action is executed.

    public function preCreate(?array $createItem = null): array|bool|null
    {
        if ($createItem) {
            $createItem['title'] = $createItem['title'] . " - " . date('Y-m-d H:i:s');
        }

        return $createItem;
    }

If this hook returns null or a false value, the create action will abort.

Also, this hook has access to the createItem that is about to be created. You can mutate data as you see fit at this point or add extra data.

On success, hooks must return the createItem that will be used to create the record.

postCreate#

This hook is called after the create action is executed.

    public function postCreate(object|array|null $createdItem = null): object|array|null
    {
        $createdItem->created = true;
        return $createdItem;
    }

It gives you access to the currently create record. You can mutate the return data as you see fit, but this won’t affect the object that has already been saved. This is just for the response.

Whatever object or array you return from here is what shall be sent back to the user.

preUpdate#

This hook is called before the update action is executed.

    public function preUpdate(?array $updateItem = null): array|bool|null
    {
        if ($updateItem) {
            $updateItem['title'] = $updateItem['title'] . " - " . date('Y-m-d H:i:s');
        }

        return $updateItem;
    }

If this hook returns null or a false value, the update action will abort.

Also, this hook has access to the updateItem that is about to be updated. You can mutate data as you see fit at this point or add extra data.

The object that is returned from this hook is what shall be used to update the record.

postUpdate#

This hook is called after the update action is executed.

    public function postUpdate(object|array|null $updatedItem = null): object|array|null
    {
        $updatedItem->updated = true;
        return $updatedItem;
    }

It gives you access to the currently updated record. You can mutate the return data as you see fit, but this won’t affect the object that has already been saved. This is just for the response.

Whatever object or array you return from here is what shall be sent back to the user.

preDelete#

This hook is called before the delete action is executed.

    public function preDelete(object|array|null $itemToDelete = null): array|null|object|bool
    {
        if ($itemToDelete->id > 10){
            return false;
        }
        return $itemToDelete;
    }

If this hook returns null or a false value, the delete action will abort. Otherwise, the $itemToDelete will be deleted.

The hook also gives you access to the item to be deleted. You can perform any conditions or any other logic you see fit.

postDelete#

This hook is called after the delete action is executed.

    public function postDelete(PDOStatement $deleteInstance, object|array|null $deletedItem = null): mixed
    {
        return $deletedItem;
    }

However much the record is nolonger in the db, this hook gives you access to the record that was deleted. You can use it as you see fit. The object that is returned from this hook is what shall be sent back to the user.

Why would you need these hooks?#

1. Hooks can be used to mutate data before it is saved to the database.
2. Hooks can be used to transform the response back to the user to meet your needs.
3. It is in these hooks where you have a chance to log, send emails or do any other action that is not directly related to the CRUD operation.

Securing Generic Services.#

The fact that Generic Services extend BaseRestService means that all authentication and authorization checks are still in place.

You can still use $serviceRequiresAuth to protect the entire service from unauthenticated access.

public bool $serviceRequiresAuth = true;

You can also define a few actions that will require authentication like below.

public ?array $actionsRequiringAuth = ['create', 'update', 'delete'];

You can also protect actions by permissions using the $actionPermissions property.

public ?array $actionPermissions = [
    'create' => ['create_student'],
    'update' => ['update_student'],
];

This will ensure that only users with the listed permissions can access the action.

Conclusion#

The generic services are there to help you with the CRUD operations. They are there to help you focus on the complex business logic.

You can use the mixin to come up with your own custom generic services. You can also override the actions provided by the generic services.

This is all to turbo charge your development process which is the main goal of Pionia.