javascript 如何知道 Backbone model.fetch() 何时完成？

How to know when a Backbone model.fetch() completes?

提问by user1031947

I bind on the change event of my backbone models like this.

我像这样绑定了我的主干模型的更改事件。

this.model.on( "change", this.render, this );

Sometimes I want to fetch the latest version of the model and forcibly render the view. So I do this

有时我想获取最新版本的模型并强行渲染视图。所以我这样做

this.model.fetch();

Unfortunately model.fetch() only fires the change event if the new data is different from what was previously stored in the model.

不幸的是，如果新数据与之前存储在模型中的数据不同，model.fetch() 只会触发更改事件。

How can I always trigger a this.render callback when fetch completes, whether it triggers a change event or not?

如何在 fetch 完成时始终触发 this.render 回调，无论它是否触发更改事件？

Thanks (in advance) for your help

在此先感谢您的帮助

回答by Ben

You can use the $.ajaxsuccess callback, but you can also just listen for the Backbone syncand errorevents on the model. syncfires after a successful call to the server, errorfires after a failed call to the server.

您可以使用$.ajax成功回调，但您也可以只侦听模型上的Backbonesync和error事件。sync在成功调用服务器后error触发，在调用服务器失败后触发。

this.model.on('sync', this.render, this);
this.model.on('error', this.handleError, this);

回答by JayC

The fetchmethod can optionally accept has success and error callbacks; the simplest solution is to put you view's renderin the success callback. You could also probably use the returned jqXHR promise, but if there's ever a case where the AJAX would be successful (per jQuery) but model initialization fails, that usage could be problematic.

该fetch方法可以选择接受具有成功和错误的回调；最简单的解决方案是将您的视图放入render成功回调中。您也可以使用返回的 jqXHR 承诺，但如果出现 AJAX 成功（根据 jQuery）但模型初始化失败的情况，则该用法可能会出现问题。

回答by Hayk Aghabekyan

I don't know what is your code structure, however if your are fetching your model inside your view, you can use something like this

我不知道你的代码结构是什么，但是如果你在你的视图中获取你的模型，你可以使用这样的东西

var that = this;
this.model.fetch().done(function () {
    that.render();
});

else, if your are fetching your model outside your view, you can pass your promise to your view and make something similar

否则，如果您在视图之外获取模型，则可以将您的承诺传递给您的视图并进行类似的操作

var promise = model.fetch();
// other code here
var view = new View({
    model: model,
    promise: promise
});

and inside your view, for example in initialize

在您的视图中，例如在初始化中

View = Backbone.View.extend({
    initialize: function(){
        this.options.promise.done(function () {
            // your code here
        });
    }
});

回答by Andrew Fedyk

How about this solution:

这个解决方案怎么样：

// emit fetch:error, fetch:success, fetch:complete, and fetch:start events
fetch: function(options) {
  var _this = this;

  options = options || {};

  var error = options.error;
  var success = options.success;
  var complete = options.complete;

  options.error = function(xhr, textStatus, errorThrown) {
    _this.trigger('fetch:error');
    if (error) error(xhr, textStatus, errorThrown);
  };

  options.success = function(resp) {
    _this.trigger('fetch:success');
    if (success) success.call(options.context, resp);
  };

  options.complete = function() {
    _this.trigger('fetch:complete');
    if (complete) complete();
  };

  _this.trigger('fetch:start');

  return Backbone.Model.prototype.fetch.call(this, options);
}

Link to gist https://gist.github.com/fedyk/23761ce1236c5673fb84

链接到要点https://gist.github.com/fedyk/23761ce1236c5673fb84