zam_command_pattern 0.2.0

Provides utilities to implement the command pattern (a behavioral design pattern).

Command Pattern

Provides utilities to implement the command pattern.

What's inside the package

• Command
• CommandFactory
• CommandExecutor

Check out all the components in detail here

How to use

// Create the base command.
abstract class CarCommand implements Command<void> {}

// Create child command StartEngineCommand.
class StartEngineCommand implements CarCommand {
  @override
  void execute() {
    print('Engine Started.');
  }
}

// Create child command ApplyBrakeCommand.
class ApplyBrakeCommand implements CarCommand {
  @override
  void execute() {
    print('Brake Applied.');
  }
}

// Now let's see the library in action.
void main() {
  // Executing a command is simple.
  final command = StartEngineCommand();
  command.execute(); // prints 'Engine Started'.

  // For complex systems you can use the executor.
  // Build the command executor.
  // Register StartEngineCommand.
  final executor = CommandExecutor.fromBuilders({
    StartEngineCommand: () => StartEngineCommand(),
  });

  // Registered command runs.
  executor.execute(StartEngineCommand); // prints 'Engine Started'.

  // Unregistered command throws error.
  try {
    executor.execute(ApplyBrakeCommand); // throws CommandNotDefinedException.
  } catch (e) {
    // CommandNotDefinedException has occured.
    // > Problem: ApplyBrakeCommand is not registered in the factory.
    // > Solution: Please add ApplyBrakeCommand to the factory.
    print(e);
  }
}

To learn more, move on to the example section or check out these dedicated examples in github.

Status

Contributors

• Amsakanna

License

BSD 3-Clause License