$.when not waiting for Ajax request to finish

问题

I want to first render a view with Backbone.js that displays an Article pulled from the server. I then want to mark this as "seen" and return the count of unseen messages to the router as it needs to be made available to other views.

So in my Router, I have:

    getArticle: function (id) {

        require(["app/models/article", "app/views/Article"], function (models, Article) {

                var article = new models.Article({id: id});

                article.fetch({
                    success: function (data) {

                        var articleView = new Article({model: data, message_count:that.message_count});

                        slider.slidePage(articleView.$el);

                        $.when(articleView.saveView()).done(function(data){
                            console.log('in when and data is ');
                            console.log(data);
                        });

                    },
                    error: function(){
                        console.log('failed to fecth artcie'); 
                    }
                });

        });
    },

saveView() in the Article view is:

    saveView: function(){

        var viewDetails = [];

        viewDetails.device_id = this.options.device_id;
        viewDetails.article_id = this.model.id;
        viewDetails.project_title = project_title;

        var article_view = new models.ArticleView();

        article_view.save(viewDetails, 
                        {
                        success: function(data) {
                                var count = data.get('count');   
                                console.log('in saveView() success and count is ');
                                console.log(count); 
                                return count;     
                            },
                            error:   function(model, xhr, options){
                               console.log(xhr.responseText);
                            },
                        });
    },

This hits a REST API, records the viewing of the article and then returns a count of unseen Articles. This results in a console output of:

in when and data is router.js:286 undefined router.js:287 in saveView() success and count is Article.js:45 4

So, somehow, $.when is not working as it's not waiting for the Ajax request to send before executing the .done script. Any ideas?

回答1:

You need to return a jQuery Deferred object for $.when to work properly:

return article_view.save(viewDetails, 
    {
    success: function(data) {
            var count = data.get('count');   
            console.log('in saveView() success and count is ');
            console.log(count); 
            return count;     
        },
        error:   function(model, xhr, options){
           console.log(xhr.responseText);
        },
    });

Backbone's save() method returns a jqXHR object which behaves the same way as a Deferred object in this case. Simply chain the return call as above. This should get $.when() to wait for the request to finish.

来源：https://stackoverflow.com/questions/21405765/when-not-waiting-for-ajax-request-to-finish