SendableChooser Lesson

SendableChooser: Selecting Your Strategy

A competitive robot needs multiple autonomous routines. The `SendableChooser` is a powerful WPILib utility that creates an interactive drop-down menu on the SmartDashboard, allowing the drive team to select the right auto for any match.

How It Works: A Three-Step Process

Implementing a `SendableChooser` is a straightforward process that takes place almost entirely inside `RobotContainer.java`. It provides a simple, reliable way to manage multiple autonomous strategies without redeploying code.

Step 1: Declare the `SendableChooser`

First, create an instance of `SendableChooser` as a private field in `RobotContainer`. Its generic type will be `Command`, since we'll be choosing between different autonomous command groups.

public class RobotContainer {
    // ... instances of subsystems ...

    // Declare the SendableChooser to hold Command objects
    private final SendableChooser<Command> m_chooser = new SendableChooser<>();

    // ... rest of the class ...
}

Step 2: Add the Autonomous Options

In the `RobotContainer` constructor, populate the chooser with your autonomous routines. Use `.addOption()` for regular choices and `.setDefaultOption()` for the crucial fallback routine.

public RobotContainer() {
    // ... other setup ...

    // Create instances of your different autonomous commands
    Command twoPieceAuto = new TwoPieceAuto(m_drivetrain, m_intake);
    Command defenseAuto = new DefenseAuto(m_drivetrain);
    Command simpleAuto = new DriveForwardAuto(m_drivetrain);

    // Add options to the chooser
    m_chooser.addOption("Two Piece Auto", twoPieceAuto);
    m_chooser.addOption("Defense Auto", defenseAuto);
    
    // Set a default option as a safety measure
    m_chooser.setDefaultOption("Simple Drive Forward", simpleAuto);

    // ... configureButtonBindings() ...
}

Step 3: Publish and Get the Selected Command

Finally, publish the chooser to the SmartDashboard and create the `getAutonomousCommand()` method that `Robot.java` will call to retrieve the drive team's selection.

public RobotContainer() {
    // ... add options to chooser ...

    // Put the chooser on the SmartDashboard
    SmartDashboard.putData("Autonomous Mode", m_chooser);

    configureButtonBindings();
}

/**
 * Use this to pass the autonomous command to the main {@link Robot} class.
 * @return the command to run in autonomous
 */
public Command getAutonomousCommand() {
    // Returns the command selected by the user on the SmartDashboard
    return m_chooser.getSelected();
}

Test Your Knowledge

Question: What is the purpose of using `.setDefaultOption()` when setting up a `SendableChooser`?