Composition Types

Repeatedly Composition

The repeatedly() decorator, backed by the RepeatCommand class restarts the command each time it ends, so that it runs until interrupted.

Decorator

Command repeats = exampleCommand.repeatedly();

The command is restarted by calling the command's execute() method again. The command is interrupted by calling the command's end() method.

Canceling a Repeatedly Command

Command repeats = exampleCommand.repeatedly();
// Assuming the command is scheduled
repeats.cancel();

Sequential Composition

Arguably one of the most important composition type, the SequentialCommand class runs a list of commands in sequence. The command ends when the last command in the sequence ends.

Sequential Compositions can be created in a variety of ways:

Using SequentialCommand Constructor.andThen() DecoratorSequentialCommandGroup Class

Command sequential = new SequentialCommand(exampleCommand, exampleCommand2);

Command sequential = exampleCommand.andThen(exampleCommand2);

Command sequential = new SequentialCommandGroup(exampleCommand, exampleCommand2, exampleCommand3);
// OR
Command sequential = new SequentialCommandGroup()

sequential.addCommands(exampleCommand, exampleCommand2, exampleCommand3);

What's the difference between a SequentialCommand and SequentialCommandGroup?

The main difference between the two is that a SequentialCommandGroup allows you to group multiple commands together as a single command. This means that you can create a complex series of actions, like moving an arm, then closing a claw, then raising the arm again, and execute them all as a single command.

Parallel Composition

Another important composition type, the ParallelCommand class runs a list of commands in parallel. The command ends when the last command in the sequence ends.

Parallel Compositions can be created in a variety of ways:

Using ParallelCommand Constructor.alongWith() DecoratorParallelCommandGroup Class

Command parallel = new ParallelCommand(exampleCommand, exampleCommand2);

Command parallel = exampleCommand.alongWith(exampleCommand2);

Command parallel = new ParallelCommandGroup(exampleCommand, exampleCommand2, exampleCommand3);
// OR
Command parallel = new ParallelCommandGroup()

parallel.addCommands(exampleCommand, exampleCommand2, exampleCommand3);

What's the difference between a ParallelCommand and ParallelCommandGroup?

ParallelCommandGroup is used when you want to group commands together as a single logical unit.
ParallelCommand is used when you want to run multiple commands independently and concurrently.

Last update: April 22, 2023
Created: April 22, 2023