class Command

Overview

Represents a single Scene option.

Commands are displayed after a Scene description, and allow the player to iteract with the game.

Keyless Commands

A command can be keyless if it has no sibling commands and you want to capture freeform text. For example you could retrieve a character's name, such as in MenuCommands::GetCharacterName.

Keyless commands don't need to be selected by typing a key (or keys) like keyed commands.

To create a keyless command simply exclude the key parameter.

Example

Command.new(description: "Tell me about yourself", scene: NextScene)

Nested Commands

Commands can be nested in order to produce complex command trees. The Scene won't change until the player exits the command tree.

Example

In this example the player is asked to enter their favorite color as freeform text. Next they must choose between two options: "apples" or "oranges". Finally, the player is take to the next scene.

Command.new(
  description: "We need to gather a little information first",
  sub_command: Command.new(
    description: "What is your favorite color?",
    sub_commands: [
      Command.new("a", "I perfer apples", NextScene),
      Command.new("o", "I perfer oranges", NextScene),
    ]
  )
)

TODO it would be nice to make the keyless and keyed command types type-safe so they are not used incorrectly.

Direct Known Subclasses

Defined in:

engine/command.cr

Constructors

Instance Method Summary

Constructor Detail

def self.new(key : String, description : String, scene : Scene.class?) #

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def self.new(key : String, description : String, sub_commands : Array(Command)) #

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def self.new(key : String, description : String, sub_command : Command) #

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def self.new(description : String, scene : Scene.class?) #

Creates a keyless command that will execute a scene right away Keyless commands should not be used with keyed commands.


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def self.new(description : String, sub_commands : Array(Command)) #

Creates a keyless command that immediately calls another command. Keyless commands should not be used with keyed commands.


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def self.new(description : String, sub_command : Command) #

Creates a keyless command that immediately calls another command. Keyless commands should not be used with keyed commands.


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Instance Method Detail

def description : String #

A description of the command. This should help the player decide what to do.


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def execute(state : State, user_input : String?) : State #

Performs extra processing on the user input. This will run for both keyed and keyless commands. Override this to add your custom logic.

When using nested commands, commands are executed in order of selection by the player.

This is one of the most important parts of a command, because it allows us to change state in response to the player's choices in the game.

Example

If we had a skill field on Character we could update it here to give our player more abilities.

def execute(state : State, user_input : String?) : State
  state.character.skill += 1
  return state
end

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def key : String? #

The character or characters that a player must enter into the terminal in order to select this command. If the key is nill the command will be automatically selected.


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def scene : Scene.class? #

The scene that will be visited next after this command has been executed. If the scene is nill and there are no #sub_commands the game will exit.


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def sub_commands : Array(Command) #

An array of sub commands available to the user. Instead of navigating directly to a scene, these subcommands will be display to the player. Then we rely on the subcommands to specify a scene to visit next.


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def validate(state : State, user_input : String?) : Bool #

Validates the user input given to the command. This is only executed for keyless commands since the input to keyed commands is always the same as their #key. Override this to add your custom logic.

You could for example, you could make sure the player does not give an empty string for their character name.


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