Conditions

Conditions let you express and verify boolean requirements within your game. For example

• Whether a player has a key in their inventory.
• Whether a door is unlocked.
• Whether it is wednesday.

In Ludiek, Conditions are an abstract Engine concept. You provide a condition shape and logic to evaluate whether this condition is true or false. At runtime, the Engine queries the registered evaluators and invokes their evaluate method.

Sounds complicated? It’s really not! Let’s take a look at the Currency Plugin. It provides the HasCurrencyCondition.

First we define the shape of what an instance of our condition should look like:

interface HasCurrencyCondition extends BaseCondition {
  type: '/condition/has-currency';
  id: string;
  amount: number;
}

And we extend a LudiekEvaluator to check whether it is true:

// This tells the engine that this evaluator depends on the currency plugin
type Dependencies = {
  plugins: [CurrencyPlugin];
};

export class HasCurrencyEvaluator extends LudiekEvaluator<HasCurrencyCondition, Dependencies> {
  readonly type = '/condition/has-currency';

  evaluate(condition: HasCurrencyCondition): boolean {
    return this.engine.plugins.currency.hasCurrency(condition);
  }
}

And we can use it fully type-safe!

game.engine.evaluate({
  type: '/condition/has-currency',
  id: '/currency/money',
  amount: 100,
});

Any game content can now use this condition as a requirement!