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Property Included in a Flow

In the fy syntax, a property is a class mixin that defines a method annotated with @property Python annotation to provide data to the encapsulating flow. Properties can be defined in various ways, depending on how the data is intended to be used or modified. For instance, a property might fetch data from a database or a third-party API, or it could compute data using other properties included in the flow.

Syntax

flow HelloWorld_UsingGreeting -> None:
    property greeting using hello_world
mixins/property/greeting/using_hello_world_fy.py
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"""fy
flow HelloWorld_UsingGreeting -> None:
    property greeting using hello_world
"""

from fy_core.base.flow_base import FlowBase

from mixins.property.greeting.using_hello_world_fy import (
    Greeting_UsingHelloWorld_PropertyMixin,
)


# fy:start ===>>>
class HelloWorld_UsingGreeting_Flow(
    # Property Mixins
    Greeting_UsingHelloWorld_PropertyMixin,
    # Base
    FlowBase[None],
):
    def __call__(self) -> None:
        # fy:end <<<===
        print(self._greeting)

Breakdown of Syntax

  1. flow HelloWorld_UsingGreeting -> None:
    • Declares a new flow named HelloWorld_UsingGreeting, which is implemented as a Python class that uses property as a mixin.
    • -> None specifies the return type of the flow, which in this case is None.
  2. property greeting using hello_world
    • Declares a property named greeting with a constant value or predefined behavior.
  3. Code Generation:
    • The fy tool generates code between # fy:start and # fy:end including the class definition and the method declaration.
    • The generated code includes the class definition HelloWorld_UsingGreeting_Flow, which incorporates the Greeting_UsingHelloWorld_PropertyMixin mixin and the FlowBase base class.
    • The Greeting_UsingHelloWorld_PropertyMixin import statement is automatically added once in the file. When the fy tool detects this import in the code, it skips adding it again to avoid disrupting the import order.
    • The declaration of __call__(self) -> None: method.
  4. User Input:
    • The only code the user needs to write is the flow declaration within the """fy block.
    • After boilerplate code generation, the user can add custom functionality, such as print(self._greeting).

Summary

In fy, defining a property in a flow allows you to encapsulate data as an attribute that is used by other property and method mixins included in a flow. A flow can include property implementation that fits its needs, like fetching data from the database or providing a constant value. This makes it easy to manage state and logic in a modular and intuitive way.