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

问题:

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

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

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.

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

Thanks (in advance) for your help

回答1:

You can use the $.ajax success callback, but you can also just listen for the Backbone sync and error events on the model. sync fires after a successful call to the server, error fires after a failed call to the server.

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

回答2:

The fetch method can optionally accept has success and error callbacks; the simplest solution is to put you view's render in 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.

回答3:

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

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

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

and inside your view, for example in initialize

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

回答4:

How about this solution:

// 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

文章来源: How to know when a Backbone model.fetch() completes?