How to re fetch backbone collection after collecti

问题:

Can someone tell me how to re fetch a Backbone collection after calling collection's create function when I create a new model?

When I call fetch on my collection after creating new model, sometimes I'm getting that model and sometimes not.

My problem is when I create a new model in my collection, I'm not getting the id back of my model and then I can't update it immediately, I need to refresh the page and then I got the id of the created model.

I tried with listenTo but I can't use it because I need to send more collections to one function.

And that my view for my bootstrap modal, on save I'm creating my model it persists to database and I'm getting all attributes in my console when I create it except models id.

Backbone view:

app.types.EditView = Backbone.View.extend({

    tagName: "div",

    $container: $('#containerEdit'),
    template: _.template($('#itemEdit-template').html()),

    events: 
    {
            "click .save": "save",
    },

    initialize: function(options)
    {   
            this.options = options;

            this.$container.html(this.render());

            this.start();
            this.end();
    },

    render: function() 
    {
            this.$el.html(this.template());
            return this.$el;
    },

    save: function() 
    {
            console.log("save");
            $('#openModal').modal('hide');
            var dan = this.model.dan_u_tjednu_usera.datum;
            var mjesec = this.model.dan_u_tjednu_usera.mjesecBrojevi;
            var godina = this.model.dan_u_tjednu_usera.godina;
            var start = $("#start").val();
            var end = $("#end").val();
            var user_id = this.model.user.id;

            this.model.shifts.create({day: dan, month: mjesec, year: godina, time_from: start, time_to: end, user_id: user_id});
            this.options.model.el.html($("<td href='#openModal' width='25%' align='center' class='list-group test' scope='row'>" + start + " - " + end + " " + "Admin" + "</td>"));
            this.model.shifts.fetch({sync: true});
            console.log("test", this.model.shifts);

    }

Here you can see that in my response im not getting the id attribute, on create.

And here you can see when i click on my cell i log my collection and i have not the id attribute of the created model here. And im not getting the id attribute it too when i log this.model

回答1:

This is because the request sent to the server when you call Collection.create is asynchronous, the Javascript code will continue to execute before the server receives and responds to the request.

If you want to have the Model updated with the ID coming back from the server, you can specify {wait: true} in the Collection.create call. This will mean that the Collection will not have the Model added straight away, but instead only when the server responds (successfully).

In this case you should not run the fetch immediately afterwards, as it will also need to wait for the create operation to complete. You should setup any following actions to trigger when the create operation has completed. Here is an example:

var model = collection.create({field: 'abc'}, {wait: true});
model.once('sync', function() { window.alert(model.id); });

回答2:

Backbone's create

Convenience to create a new instance of a model within a collection. Equivalent to instantiating a model with a hash of attributes, saving the model to the server, and adding the model to the set after being successfully created.

There's no need to fetch a collection after a create, the model id and any other field are automatically merged within its attributes hash.

Fetch after model creation

While mikeapr4 is not wrong, his example could be improved.

The { wait: true } is unnecessary if the only problem comes from the fetch, not from the model already being inside the collection.

Also, once should be avoided as it's the "old" way, and instead listenToOnce should be used. See Difference between ListenTo and on.

If you really want to fetch once a model is created, using events is overkill here, and instead, using the success callback is best:

save: function() {
    // ..snip...
    this.model.shifts.create({ /* ...snip... */ }, {
        context: this,
        success: this.onModelCreated
    });
},

onModelCreated: function() {
    // the model is now created and its attributes are up-to-date
    this.model.shifts.fetch();
}

Other notes on your code

There are no sync option in Backbone. Only a "sync" event and a sync function.

---

Avoid using the global jQuery selector (like $('.class-name')) and instead, whenever the element is within the view's element, use this.$('.class-name').

Also, cache the jQuery element to avoid the costly search of the find method.

Like $("#start") could be cache and reused. Only reset the cached elements when re-rendering.

---

The Backbone .render function should return this by convention.

Then, your rendering call should look like:

this.$container.html(this.render().el); // el is enough