Summary of Design Patterns in Embedded Rust

The "Design Patterns" chapter from the Rust Embedded Book introduces various design patterns that are crucial for developing embedded systems using Rust. These patterns enhance code structure, making it more manageable, reusable, and easier to understand.

Key Concepts

• Design Patterns: Reusable solutions to common problems in software design. They provide a template to help developers create robust and efficient code.
• Embedded Systems: Specialized computing systems that perform dedicated functions within larger systems.

Main Design Patterns Covered

1. Singleton Pattern

• Purpose: Ensure that a class has only one instance and provide a global point of access to it.
• Use Case: Managing hardware resources like a sensor or a communication interface.

struct Sensor {
    // sensor fields
}

impl Sensor {
    fn instance() -> &'static mut Sensor {
        static mut INSTANCE: Sensor = Sensor { /* fields */ };
        unsafe { &mut INSTANCE }
    }
}

2. State Pattern

• Purpose: Allow an object to alter its behavior when its internal state changes.
• Use Case: Managing different states of a device, like power modes (on, off, sleep).

trait State {
    fn handle(&self);
}

struct OnState;
struct OffState;

impl State for OnState {
    fn handle(&self) {
        // logic for ON state
    }
}

impl State for OffState {
    fn handle(&self) {
        // logic for OFF state
    }
}

3. Observer Pattern

• Purpose: Define a one-to-many dependency between objects, so that when one object changes state, all its dependents are notified.
• Use Case: Event-driven systems where multiple components need to respond to an event.

struct EventEmitter {
    listeners: Vec>, 
}

impl EventEmitter {
    fn subscribe(&mut self, listener: F)
    where
        F: Fn() + 'static,
    {
        self.listeners.push(Box::new(listener));
    }

    fn emit(&self) {
        for listener in &self.listeners {
            listener();
        }
    }
}

4. Command Pattern

• Purpose: Encapsulate a request as an object, allowing for parameterization of clients with queues, requests, and operations.
• Use Case: Remote control of devices where commands need to be queued or logged.

trait Command {
    fn execute(&self);
}

struct TurnOnCommand {
    device: Device,
}

impl Command for TurnOnCommand {
    fn execute(&self) {
        self.device.turn_on();
    }
}

Conclusion

Understanding and implementing these design patterns can greatly enhance the quality of embedded systems development in Rust. They provide structured approaches to tackle common challenges, leading to cleaner and more maintainable code. As you engage more with embedded Rust, consider which patterns can be applied to your projects to improve design and functionality.