02_katoDispatcher.ts

    const onDispatch = (action: Event) => {
      switch(action.type) {
        case GreetingActionTypes.ADD_GREETING:
          let payload1 = (<AddGreetingEvent> action).payload;
          this._state.newGreeting = '';
          this._state.greetings = this._state.greetings.concat(payload1);
          this.emitChange();
          break;
        case GreetingActionTypes.REMOVE_GREETING:
          let payload2 = (<RemoveGreeting> action).payload;
          this._state.greetings = this._state.greetings.filter(g => g !== payload2);
          this.emitChange();
          break;
        case GreetingActionTypes.NEW_GREETING_CHANGED:
          let payload3 = (<NewGreetingChanged> action).payload;
          this._state.newGreeting = payload3;
          this.emitChange();
          break;
      }
    }