dev/js/src-lib/state/state.js

/**
 * Create a state object, that can have a single value
 * (mostly boolean) and multiple objects associated to it.
 * Whenever the state changes, all objects are informed
 * by their setState() method of the value change.
 *
 * @author Nils Diewald
 */
/*
 * TODO:
 *   Require names for states, that should be quite short, so they
 *   can easily be serialized and kept between page turns (via cookie
 *   and/or query param)
 */

export default class State {

  /**
   * Constructor
   */
  constructor (values) {
      this._init(values);
  }


  // Initialize
  _init (values) {
      const t = this;
      t._assoc = [];
      if (values == undefined) {
        t.values = [false,true];
      }
      else if (Array.isArray(values)) {
        t.values = values;
      }
      else {
        t.values = [values];
      }
      return t;
  }


  /**
   * Associate the state with some objects.
   */
  associate (obj) {

      // Check if the object has a setState() method
      if (obj.hasOwnProperty("setState")) {

        this._assoc.push(obj);
        if (this.value != undefined) {
          obj.setState(this.value);
        };
      } else {
        console.log("Object " + obj + " has no setState() method");
      }
  }


  /**
   * Set the state to a certain value.
   * This will set the state to all associated objects as well.
   */
  set (value) {
      if (value != this.value) {
        this.value = value;
        this._assoc.forEach(i => i.setState(value));
      };
  }


  /**
   * Set the state to a default value.
   * This will only be set, if no other value is set yet.
   */
  setIfNotYet (value) {
      if (this.value == undefined) {
        this.set(value);
      };
  }


  /**
   * Get the state value
   */
  get () {
      if (this.value == undefined) {
        this.value = this.values[0];
      };

      return this.value;
  }


  /**
   * Get the number of associated objects
   */
  associates () {
      return this._assoc.length;
  }


  /**
   * Clear all associated objects
   */
  clear () {
      return this._assoc = [];
  }


  /**
   * Roll to the next value.
   * This may be used for toggling.
   */
  roll () {
      let next = 0;
      for (let i = 0; i < this.values.length - 1; i++) {
        if (this.get() == this.values[i]) {
          next = i+1;
          break;
        };
      };
      this.set(this.values[next]);
  }
}