Call model.toJSON always when sync model

[AriasBros]

When you save your model with patch option to true, toJSON isn't called. This behavior goes against the issue #1019 where it tells that:

toJSON is already the complement of parse

With this PR the default behavior is the same as the current one, but it gives us the opportunity to manipulate the attributes before send them to the persistence layer, either using a POST, PATCH or PUT method.

[ogonkov]

If you have to manipulate attributes before sending, why not pass already manipulated object in attrs?

[AriasBros]

If you have to manipulate attributes before sending, why not pass already manipulated object in attrs?

Because the object attrs should store data in the format that is consumed by your application, not in the format of your persistence layer.

And, if toJSON is the complement of parse, it should be called always before send data to the persistence layer, in the same way that parse is always called when data is received from the persistence layer.

For example, a model with the next parse implementation:

parse(response, options) {
    response.rating = response.rating * 2;
    return response;
}

In the persistence layer, rating is stored as an integer from 0 to 5. But in our app we use rating as a number from 0 to 10.

Now, we want update the rating in our model:

model.save({ rating: 7 }, { patch: true });

Currently, with this line, our model will be updated to rating 7. And the persistence layer also will receive a 7 as rating, which is wrong. This is failing also in the premise that toJSON is the complement of parse, because it is not being called.

You are suggesting to do:

model.save({ rating: 7 / 2 }, { patch: true });

Which is also wrong, because yes, your persistence layer will receive a rating of 3.5, that is the expected value. But your model will have a rating of 3.5 too, and that value is not what you want in your application.

With this PR, in the same way that we have a parse method in our model, we will have the toJSON method too:

toJSON(options) {
    let attributes = Backbone.Model.prototype.toJSON.apply(this, arguments);
    attributes.rating = attributes.rating / 2;

    return attributes;
}

[ogonkov]

Very neat. Now it make a sense for me. Thank you for a great explanation.

[ogonkov]

It is great PR, but i think we should add some flag, to switch for new behaviour, because it is pretty much could break someones apps

Backbone.useToJSON = false;

[jgonggrijp]

@ogonkov I agree with you, but I think I want this behavior to be the default in a future Backbone 2.0. How about we name the flag Backbone.future instead of Backbone.useToJSON, and then potentially also use that flag for other behaviors that we want to change in the future?

[ogonkov]

One flag for few features? @jgonggrijp

[jgonggrijp]

Well, changed features. That we intend to become standard.