如何在服务中封装单个事件和时间事件? [英] How to encapsulate single and temporal events in a service?

问题描述

我正在尝试将事件封装在服务中，以便在控制器的作用域被破坏时实现订阅/取消订阅侦听器的机制.这是因为我一直在以下列方式使用 rootScope.$on:

I'm trying to encapsulate the events in a service in order to implement a mechanics to subscribe / unsubscribe the listeners when a controller's scope is destroyed. This because I have been using the rootScope.$on in the following way:

if(!$rootScope.$$listeners['event']) {
    $rootScope.$on('event', function(ev, data){
        // do some...
    });
}

或

$scope.$on('$destroy', function(ev, data){
    // unsubscribe the listener
});

所以我只需要这个事件的一个监听器，当控制器不再活动时，我需要删除现有的监听器，因为我之前注册的函数还在被触发.

So I just need one listener of this event, I need to delete the existing listener when the controller is no longer alive, because the function I registered earlier is still being triggered.

所以我需要在我的控制器上实现一个 $destroy 事件监听器，以便在作用域被销毁时销毁监听器，但我不想每次创建事件时都执行该代码.这就是为什么我要创建一个服务来封装事件.

So I need to implement a $destroy event listener on my controller, to destroy the listener when the scope is destroyed, but I don't want to do that code each time I create an event. That's why I want to create a service in where I'm going to encapsulate the events.

angular.module('core').factory('event', [
    function() {
        var service = {};
        service.events = {};
        service.on = function(scope, eventId, callback) {
            scope.$on('$destroy', function(ev, other){
                //unsubscribe
            });
            service.events[eventId] = callback;
            // scope = null; I guess ?
        };
        service.emit = function(eventId, data){
            if (service.events[eventId])
                service.events[eventId](data);
            else
                return new Error('The event is not subscribed');
        };
        return service;
    }
]);

这可以使用 $rootScope 而不是我自己的方法来完成，但是封装了 $rootScope 的 $on 和 $emit，但最后我会在这里遇到同样的问题.

This could be done using $rootScope instead of my own methods but encapsulating the $on and $emit of $rootScope, but at the end I'll have the same issue here.

所以这些是我的问题:

1. 将范围引用值传递给服务是一种好的做法吗?
2. $$destroyed 是什么意思?当这是真的意味着 angularJS 没有对实例的内部引用?
3. 我应该在我的服务中做一个 scope = null 来让 GC 删除对象还是 angularJS 处理显式删除?
4. 有没有更好的方法来做我想做的事?

1. Is a good practice to pass the scope ref value to a service?
2. What is the meaning of $$destroyed? when this is true means that angularJS has no internal references to the instance?
3. Should I do a scope = null in my service to let GC delete the object or does angularJS handle an explicit delete?
4. Is there a better way to do what I want?

推荐答案

你想要完成的基本上是一个事件总线.
您还很好地描述了当前实现的问题.解决这个问题的另一种方法是用你的总线(或任何其他事件总线)装饰 $rootScope .方法如下:

What you are trying to accomplish is basically an event bus.
You have also described very well what is wrong with the current implementation. A different way to approach the problem is to decorate the $rootScope with your bus (or any other event bus for that matter). Here is how:

app.config(function ($provide) {
$provide.decorator('$rootScope', ['$delegate', '$$bus', function ($delegate, $$bus) {
  Object.defineProperty($delegate.constructor.prototype, '$bus', {
    get: function () {
      var self = this;

      return {
        subscribe: function () {
          var sub = $$bus.subscribe.apply($$bus, arguments);

          self.$on('$destroy',
            function () {
              console.log("unsubscribe!");
              sub.unsubscribe();

            });
        },

        publish: $$bus.publish
      };
    },
    enumerable: false
  });

  return $delegate;
}]);
});

考虑以下 $$bus 实现(为简单起见保持基本):

Considering the following $$bus implementation (kept basic for simplicity):

app.factory('$$bus', function () {
  var api = {};
  var events = {};

  api.subscribe = function (event) {
    if (!events.hasOwnProperty(event.name)) {
      events[event.name] = [event];
    } else {
      events[event.name].push(event);
    }
    return {
      unsubscribe: function () {
        api.unsubscribe(event);
      }
    }
  };

  api.publish = function (eventName, data) {
    if (events.hasOwnProperty(eventName)) {
      console.log(eventName);

      angular.forEach(events[eventName], function (subscriber) {
        subscriber.callback.call(this, data);
      });
    }
  };

  api.unsubscribe = function (event) {
    if (events.hasOwnProperty(event.name)) {
      events[event.name].splice(events[event.name].indexOf(event), 1);
      if (events[event.name].length == 0) {
        delete events[event.name];
      }
    }
  };

  return api;
});

现在您要做的就是订阅或发布事件.取消订阅将自动发生(当 $scope 被销毁时):

Now all you have to do is subscribe or publish events. The unsubscribe will take place automatically (when the $scope is destroyed):

  $scope.$bus.subscribe({
    name: 'test', callback: function (data) {
      console.log(data);
    }
  });

然后发布一个事件:

  $scope.$bus.publish('test', {name: "publishing event!"});

要说明的重要点是事件本身订阅到每个单独的 $scope 而不是 $rootScope.这就是你知道"要释放哪个 $scope 的方式.

An important point to make is that the events themselves are subscribed to each individual $scope and not on the $rootScope. That is how you "know" which $scope to release.

我认为它回答了您的问题.考虑到这一点，您显然可以使这种机制更加复杂(例如在视图路由时释放控制器事件侦听器，仅自动取消订阅某些事件等).祝你好运！

I think it answers your question. With that in mind, you can obviously make this mechanism much sophisticated (such as controller event listener released when a view routed, unsubscribe automatically only to certain events, etc.). Good luck!

** 此解决方案采用 此处使用不同的总线框架(除此之外它是相同的).

** This solution is taken form Here which uses a different bus framework (other then that it is the same).

这篇关于如何在服务中封装单个事件和时间事件?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！