Using $watch without $scope ( controller as syntax

问题:

In Angular 1.3 it's possible to use this.foo='bar' insteaod of $scope.foo='bar'. Now, how can I use $watch without $scope?

回答1:

There are several options to avoid having to use $watch when using the controller as syntax.

The following examples are taken from a blog post I wrote about avoiding $scope.

Using ng-change

If you have a watch set up to listen for a property change that originates from a form field, then ng-change is your best bet.

<input type="text" ng-model="ctrl.name" ng-change="ctrl.search(ctrl.name)" />

MyCtrl.prototype.search = function(name){
  //call some service here
};

Using ES5 Properties

If you have some property that isn't bound to an input field, or is going to be updated from code, it may seem like a watch is your only choice. However, if you don't have to support IE8 or lower, then you can take advantage of ES5 properties to trigger functionality when something changes on your controller.

var MyCtrl = function(){
  this._selectedItem = null;
};

Object.defineProperty(MyCtrl.prototype,
    "selectedItem", {
    get: function () {
        return this._selectedItem;
    },
    set: function (newValue) {
        this._selectedItem = newValue;

        //Call method on update
        this.onSelectedItemChange(this._selectedItem);
    },
    enumerable: true,
    configurable: true
});