Command Pattern

Conceptual overview of the "what" and "why" of Command pattern

The Command pattern is a fundamental design principle FTCLib uses, and understanding it will significantly enhance your coding experience. This page delves into the "what" and "why" behind this pattern, equipping you to write efficient and maintainable robot code.

https://docs.ftclib.org/ftclib/

What is Command Pattern?

The Command pattern boasts a rich history dating back to the late 1970s and early 1980s. The concept emerged within the Smalltalk and Xerox PARC communities, documented in publications like Anneliese Schürr's 1992 paper "Separation of Concerns and the Command Pattern." Initially focused on graphical user interfaces (GUIs), the pattern's flexibility was adopted in various software development domains.

Its popularity soared with the rise of design patterns in the 1990s, solidified by Erich Gamma et al.'s influential book "Design Patterns: Elements of Reusable Object-Oriented Software." This widespread recognition cemented the Command pattern as a valuable tool for promoting loose coupling, reusability, and maintainability in object-oriented programming.

Gamma, Helm, Johnson and Vlissides are sometimes referred to as the Gang of Four or GoF

The Command pattern originates from software design principles and offers a structured way to manage robot actions. Instead of writing long, blocking code sections, you create independent classes called Commands. Each Command encapsulates your robot's specific task, like driving forward, turning, or activating a mechanism.

Why Command Pattern?

Farewell, Blocking Code

Traditional robot programming often involves lengthy code blocks that execute sequentially, potentially hindering responsiveness and multitasking. If your robot is stuck inside of a loop that gradually moves a motor, it's not doing other things. It's blocked until you move on.

Non-blocking commands eliminate the need to do one thing at a time by having repeatedly called execute functions that run until their isFinished condition is reached. This allows the robot to perform multiple actions simultaneously. This means smoother operation and the ability to react to real-time events effectively.

Reusable Gems

Commands are designed for reusability. You can create a generic RotateCommandand adapt it for different distances or speeds across various parts of your code. This reduces code duplication and simplifies maintenance.

Collaborative Codebase

FTCLib encourages modularity with separate Command files. This translates to clear ownership and promotes a collaborative development environment. Team members can work on their specific Commands without worrying about conflicts in common code sections. Version control systems like Git become even more valuable as team members push their Command commits independently.

Utilities in FTCLib

FTCLib does much more than implement the Command pattern. We've got ourselves an extensive toolbox to elevate our robot programming:

Finer Motor Control:

• Motor Wrappers: Simplify motor control with pre-built classes handling direction, speed, and encoder feedback.

• PID Control Helpers: Fine-tune motor movements with built-in PID controllers for precise control.

Navigation Expertise:

• Odometry Support: Implement robust navigation using odometry wheels. FTCLib calculates robot pose from encoder readings, simplifying movement and autonomous routines.

• Path Following: Define and execute pre-defined paths for complex maneuvers and automated navigation.

Visionary Solutions:

• EasyOpenCV Integration: Seamlessly incorporate computer vision tasks. Detect objects, track targets, and analyze the environment using EasyOpenCV's intuitive tools.

• Camera Support: Access and manage multiple cameras on your robot, expanding your visual perception capabilities.

Sensor Fusion Power:

• Sensor Wrappers: Interact easily with various sensors like gyros, accelerometers, and ultrasonic sensors. Access their data effortlessly for informed decision-making.

• Data Fusion: Combine data from multiple sensors to better understand your robot's environment, enabling intelligent responses.

Additional Gems:

• Telemetry: Log and display robot data on the Driver Station for debugging, monitoring, and optimization.

• Logging: Record robot behavior for analysis and performance improvements.

• Scheduling: Manage task execution precisely with the built-in scheduler, ensuring coordinated robot actions.

Video Overview