Modules¶
A module in Ellar is essentially a class marked with the @Module()
decorator. This simple yet powerful annotation serves as the cornerstone of defining the architecture and organization of an application.
Embracing the modular approach, each module encapsulates a specific set of functionalities, ensuring a clear separation of concerns within the application. The ApplicationModule
typically acts as the root module, orchestrating the composition of various submodules.
This modular structure enables efficient management of dependencies, promotes code reusability, and enhances maintainability by facilitating clear boundaries between different components of the application. By structuring the application into modules, developers can easily reason about the codebase, foster collaboration among team members, and scale the application seamlessly.
Feature modules¶
Developing an application as a collection of feature modules grouped together offers several advantages. It helps in managing complexity, maintains a codebase that is both extendable and testable, and promotes adherence to SOLID principles.
A prime example of a feature module is the car project. In this project, the CarModule
encapsulates all the services and controllers responsible for handling the car
resource. This modular structure simplifies maintenance, extension, and testing of the codebase.
# project_name/apps/car/module.py
from ellar.common import Module
from ellar.core import ModuleBase
from ellar.di import Container
from .services import CarRepository
from .controllers import CarController
@Module(
controllers=[CarController],
providers=[CarRepository],
)
class CarModule(ModuleBase):
def register_providers(self, container: Container) -> None:
# Additional provider registrations can be done here
pass
Module Parameters¶
Let's create a Module and take a quick overview of its parameters.
from ellar.common import Module
from ellar.core import ModuleBase
@Module(
name='',
modules=[],
providers=[],
controllers=[],
routers=[],
commands=[],
base_directory=None,
static_folder='static',
template_folder='templates'
)
class BookModule(ModuleBase):
pass
Parameter | Description |
---|---|
name | The name of the module. It's relevant for identification purposes. |
modules | A list of dependencies required by this module. |
providers | Providers to be instantiated by the Ellar injector, possibly shared across this module. |
controllers | Controllers defined in this module that need instantiation. |
routers | ModuleRouters defined in this module. |
commands | Functions decorated with EllarTyper or command that serve as commands. |
base_directory | The root directory for this module, used to locate static_folder and template_folder . Default is the module's root. |
static_folder | The folder for static files within this module. Default is 'static'. |
template_folder | The folder for templates within this module. Default is 'templates'. |
Additional Module Configurations¶
The Ellar framework offers additional module configurations to handle various aspects of the application lifecycle and behavior.
Module Events¶
Modules can define before_init
class method to configure additional initialization parameters before instantiation. This method receives the current application config as a parameter, allowing for further customization.
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Module Application Cycle¶
Ellar follows a two-phase application lifecycle with on_startup
and on_shutdown
events managed by EllarApplicationLifespan
.
from ellar.common import Module, IApplicationShutdown, IApplicationStartup
from ellar.core import ModuleBase
@Module()
class AModuleSample(ModuleBase, IApplicationStartup):
async def on_startup(self, app: "App") -> None:
pass
@Module()
class BModuleSample(ModuleBase, IApplicationShutdown):
async def on_shutdown(self) -> None:
pass
@Module()
class CModuleSample(ModuleBase, IApplicationStartup, IApplicationShutdown):
async def on_startup(self, app: "App") -> None:
pass
async def on_shutdown(self) -> None:
pass
Module Exceptions¶
Modules can register custom exception handlers for specific HTTP error codes.
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Module Templating Filters¶
Define Jinja2 templating filters within modules, which are then added to the Jinja2 environment instance during template loading.
from ellar.common import Module, template_global, template_filter
from ellar.core import ModuleBase
@Module()
class ModuleTemplateFilterSample(ModuleBase):
@template_filter()
def double_filter(cls, n):
return n * 2
@template_global()
def double_global(cls, n):
return n * 2
@template_filter(name="dec_filter")
def double_filter_dec(cls, n):
return n * 2
These configurations enhance the flexibility and functionality of Ellar modules, allowing for greater control over application behavior and lifecycle events.
Dependency Injection¶
A module class can inject providers, such as configuration objects, for various purposes. Let's consider an example from our sample project where we inject Config
into the CarModule
.
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In this example, the CarModule
class accepts a Config
object in its constructor. This allows us to access configuration parameters within the module. Additionally, the register_providers
method can be utilized for more advanced provider registrations within the container.
Module Middleware¶
Middleware functions can be defined at the module level using the @middleware()
function decorator. Let's illustrate this with an example:
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Key points to remember: - Middleware functions must be asynchronous (async
). - Middleware functions can return a response or modify a response returned. - Middleware functions must call call_next()
and await its actions as demonstrated above.
Injector Module¶
The EllarInjector
module, built on top of the Python library injector
, offers similar features to the injector
library, with some additional capabilities. One such feature is the ability to create or reuse modules from injector
Modules for configuring bindings and providers for dependency injection.
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In this example, the ExampleModule
registers the Description
and Name
types with the injector. These can then be resolved if required by any object in the application.
For more details on the use cases of the injector
module, you can refer to the documentation here.