ESPressio Observable

Synchronous Observer Pattern components for the Flowduino ESPressio Development Platform.

Latest Stable Version

3.0.0

ESPressio Development Platform

ESPressio is a collection of discrete, composable component libraries built around a common development ethos:

• Light-weight --- minimise memory consumption and runtime overhead without sacrificing correctness.
• Ease of use --- provide strongly typed, developer-friendly abstractions over lower-level facilities.
• Object-oriented --- a type for everything, and everything in a type.
• SOLID --- favour focused responsibilities, extensibility, substitutable abstractions, narrow interfaces, and dependency inversion wherever practical on embedded C++ platforms.

License

Licensed under the Apache License 2.0. See LICENSE.

ESPressio Library Dependencies

ESPressio is designed as a modular ecosystem of independently useful libraries, with required dependencies kept explicit and optional integrations introduced only when the corresponding functionality is selected.

For a complete overview of required dependencies, opt-in dependencies, and the overall hierarchy, see:

ESPressio Library Dependency Chart

• Solid relationships represent required ESPressio dependencies.
• Dashed relationships represent opt-in dependencies introduced only by the corresponding feature, integration, type, or header.

Required ESPressio dependencies

None.

Namespace

ESPressio::Observable

Observer Pattern

Observable is intended for synchronous relationships between an operation and interested observers:

Observable
   +--> Observer A
   +--> Observer B
   +--> Observer C

A subsystem normally defines a focused Observer interface derived from the library's IObserver contract and exposes registration through its Observable surface.

Registration lifetime

Version 3.x uses ownership-safe registration handles. Registrations can be explicitly removed and naturally follow the lifetime of their registration handles.

Observers remain non-owning: the application must keep an Observer alive for as long as it remains registered.

Synchronous semantics

Observer callbacks execute synchronously as part of the notifying operation.

Use Observable when the notification belongs directly to the operation and an asynchronous task boundary is undesirable.

Use ESPressio Event when producers and consumers should be independently scheduled.

Relationship with ESPressio Event

Observable does not depend on Event.

Higher-level bridges may consume synchronous Observer callbacks and emit asynchronous Events:

Timing / Threads
    -> Observable callback
    -> optional Event bridge
    -> asynchronous Event

This dependency direction keeps foundational libraries independent.

Design goals

• Focused Observer contracts.
• Explicit registration lifetime.
• Non-owning Observer relationships.
• Synchronous deterministic notification.
• Reusable infrastructure.
• No dependency on ESPressio Event.