Custom Commands

While NextFTC includes many useful commands, you often will need to create your own.

The recommended way to create a command is by using the LambdaCommand class, which allows you to define the command's behavior using lambda functions. This approach is concise and flexible, making it easy to create custom commands without needing to create a new class for each command.

Here is how the builtin RunToPosition command could be implemented using LambdaCommand:

public static Command runToPosition(ControlSystem system, double position, KineticState tolerance) {
    return new LambdaCommand("RunToPosition(" + position + ")")
            .setStart(() -> system.setGoal(new KineticState(position)))
            .setIsDone(() -> system.isWithinTolerance(tolerance))
            .requires(system);
{

Because Java doesn't have default parameters, we must make another method to use a default tolerance. This example uses a tolerance of 10.0:

public static Command runToPosition(ControlSystem system, double position) {
    return runToPosition(system, position, new KineticState(10.0));
}

The setStart, setUpdate, setIsDone, and setStop methods directly map to the methods of the Command class.

In general, a lambda command can be created as follows:

val myLambdaCommand = LambdaCommand()
    .setStart { 
        // Runs on start
    }
    .setUpdate { 
        // Runs on update
    }
    .setStop { interrupted ->
        // Runs on stop
    }
    .setIsDone { true } // Returns if the commmand has finished
    .requires(/* subsystems the command implements */)
    .setInterruptible(true)
    .named("My Command") // sets the name of the command; optional

TIP

All functions are completely optional. You only need to call the ones you will use. They can be called in any order.

Command Classes

Commands as Classes

It is unlikely that you will need to use this very often, but you can also create a command as a class. This is useful for cases where you need to reuse your command a lot. An command can be created as a class as follows:

class MyCommand(): Command() {

    init {
        requires(/* subsystems */)
        setInterruptible(true) // this is the default, so you don't need to specify
    }

    override val isDone: Boolean
        get() = false // whether or not the command is done

    override fun start() {
        // executed when the command begins
    }

    override fun update() {
        // executed on every update of the command
    }

    override fun stop(interrupted: Boolean) {
        // executed when the command ends
    }
}