How backbonejs models handle server side errors?

Question

How backbonejs models handle server side errors?

When Im sending json with errors array, im still get a success callback with errors array inside response parameter.

Answer 1

In my client-side code I check for the presence of the errors attribute and react as necessary.

For example, I was using the Collection.create function, which calls the add function of the Collection if the request was successful. So, I overrode my Collection's add function to prevent the model from being added if it has an 'errors' attribute, and if it doesn't call the "super" method.

add: function(object, options) {
    if (_.isArray(object) || !object.get('errors')) {
        Backbone.Collection.prototype.add.call(this, object, options)
    }
},

Having my app return a non-success status code would work too, as it prevents success callbacks from being run. But, I didn't like the idea of returning a 400 error just because the submission was invalid. That's something I've never had to do in non-Backbone.js apps. ("Invertebrates"?)

None of the descriptions for 4XX status codes seemed to really match the concept of failed validation. 400 and 403 come close, but still come off as if they were intended for other uses. On the other hand, the user really doesn't care what status code you return; might as well be a 404.

It's really a matter of whether you want to write more code server-side or client-side. My application more or less ignores the outcome of validation and returns the record serialized to JSON whether it was saved or not, so I chose to work from that angle.

Answer 2

Server side backbone validation:

Server side

Return errors array

Client side

Pass "wait: true" as option when calling model.save:

modelVar.save(data,{ // here be options
    wait: true,
    success: this.processRequest,
    error: this.processErrors
});

Update the model's validate function to check for the errors array:

validate: function(attrs) {
    this.errors = [];
    if (attrs.errors && attrs.errors.length > 0) {
        for (var key in attrs.errors) {
            this.errors.push(attrs.errors[key].errorMessage);
        }
    }
    return _.any(this.errors) ? this.errors : null;
}

Outcome

The error callback will run and the model will not "change" if the server retruns [errors].

UPDATE:

As of version 0.9.10 this will no longer work. You should either use the "invalid" event or use the new options argument of the model.validate(attributes, options) function: if (typeof(options.error === 'function')) options.error();