AngularJS：如何看服务的变量？ [英] AngularJS : How to watch service variables?

问题描述

我有一个服务，说：

factory('aService', ['$rootScope', '$resource', function ($rootScope, $resource) {
  var service = {
    foo: []
  };

  return service;
}]);

和我想用富来控制在HTML渲染列表：

And I would like to use foo to control a list that is rendered in HTML:

<div ng-controller="FooCtrl">
  <div ng-repeat="item in foo">{{ item }}</div>
</div>

为了使控制器检测到何时 aService.foo 更新我已经拼凑这种模式在这里我想补充aService到控制器的 $范围，然后用 $ $范围腕表（）：

In order for the controller to detect when aService.foo is updated I have cobbled together this pattern where I add aService to the controller's $scope and then use $scope.$watch():

function FooCtrl($scope, aService) {                                                                                                                              
  $scope.aService = aService;
  $scope.foo = aService.foo;

  $scope.$watch('aService.foo', function (newVal, oldVal, scope) {
    if(newVal) { 
      scope.foo = newVal;
    }
  });
}

这感觉长手，我已经在使用该服务的变量，每个控制器一直在重复它。有没有更好的方式来完成观看共享变量？

This feels long-handed, and I've been repeating it in every controller that uses the service's variables. Is there a better way to accomplish watching shared variables?

推荐答案

您可以随时，如果你想避免 $观看。

You can always use the good old observer pattern if you want to avoid the tyranny and overhead of $watch.

在该服务：

factory('aService', function() {
  var observerCallbacks = [];

  //register an observer
  this.registerObserverCallback = function(callback){
    observerCallbacks.push(callback);
  };

  //call this when you know 'foo' has been changed
  var notifyObservers = function(){
    angular.forEach(observerCallbacks, function(callback){
      callback();
    });
  };

  //example of when you may want to notify observers
  this.foo = someNgResource.query().$then(function(){
    notifyObservers();
  });
});

和控制器：

function FooCtrl($scope, aService){
  var updateFoo = function(){
    $scope.foo = aService.foo;
  };

  aService.registerObserverCallback(updateFoo);
  //service now in control of updating foo
};

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