CODEWITHSUNDEEP
backbone.jsbackbone-viewsbackbone-eventsbackbone-model
nachtigall
nachtigall

Reputation: 2497

Don't call render() if the View itself updated Model via Backbone.Model.set()

In my Backbone.js project I have one Model and several Views. All Views have registered callbacks for 'change:currentTextTitle' on this model:

// 'this' stands for any of the Views here
myModel.on('change:currentTextTitle', this.render, this);

Now a user performs some action, which causes the specific View to change its "current text title" field. This specific view then calls myModel.set("currentTextField", newTextValue) which in turn triggers the 'change:currentTextTitle' event calling all Views (including the one from which set() originated). Then all Views call their render callback functions.

The problem is that the render method is also called on the View from which the set()-Method was originally called, which is completely unnecessary because it is already up-to-date with currentTextTitle.

How would my Views call myModel.set() in a way that the other Views' callbacks get informed, but without triggering/calling the "source View" itself?

One workaround seems to be to pass the source view as part of the options parameter of the set() method (which gets passed along to trigger() and then along the the render() callback): 

myModel.set("currentTextField", newTextValue, thisViewSetAttribute)

Then in the render callback one could check if thisViewSetAttribute != this. However, instead of implementing checks in every callback, I think it would make more sense to handle this in the Model itself by only calling the necessary callbacks and ignoring the source View from which the set() method call originated. Is this possible?

Upvotes: 0

Views: 708

Answers (1)

Paul Hoenecke
Paul Hoenecke

Reputation: 5060

I think the 'proper' MCV solution is that your views should not know or care how the model changed, they should simply handle the change and update accordingly. If they are already current, the user shouldn't know the difference.

I definitely would not pass the source view to the model. Instead when the model changes, you could just have the view check if it is current and not re-render. But if the extra render doesn't cause any issues then just let it happen :)

In Backbone, the 'view' is both view and controller. So try to treat the change as 2 separate steps. First, convert user input into changes on the model, then as a separate step (initiated by model change event), handle that change and update the view. If each view does this, no matter how the model changes, everything will stay up-to-date.

Upvotes: 1

Related Questions