类语法中的$watch无法工作

Question

当页面使用以下代码加载时，手表才首次工作：

import angular from 'angular';

import '../style/app.css';

class AppCtrl {

  constructor($scope) {
    this.url = 'https://github.com/preboot/angular-webpack';
    this.val = 0;
    this.even = true;
    this.scope = $scope;    
    this.scope.$watch('val', this.valChanged());

  }

  inc() {
    this.val++;
    this.even = this.val % 2 == 0 ? true : false;     
  }

  valChanged(newVal, oldVal) {
    console.log('changed');
  }
}

AppCtrl.$inject = ['$scope'];

const MODULE_NAME = 'app';

angular.module(MODULE_NAME, [])
  .controller('AppCtrl', AppCtrl);

export default MODULE_NAME;

每当我单击调用inc()方法的按钮时，都会更新值，但不会触发valChanged方法。

使用angularjs诉1.5

Answer 1

this.scope.$watch(() => this.val, 
                 (newVal, oldVal) => this.valChanged(newVal, oldVal));