onFinishChange(fnc) {
    this.__onFinishChange = fnc;
    return this;
  }
Specify that a function fire every time someone "finishes" changing
the value wih this Controller. Useful for values that change
incrementally like numbers or strings.

@param {Function} fnc This function will be called whenever
someone "finishes" changing the value via this Controller.
@returns {Controller} this