Sorting new item creates empty object from mapping plugin

[wjbryant]

Sorting new item creates empty object from mapping plugin

[wjbryant]

Also, note that simply adding an item does not cause this problem. It's only after it's moved that the output becomes incorrect.

Using the mapping plugin directly on the items array instead of its containing object when initializing the viewModel fixes this problem. This is pretty much the same "fix" as before, except doing it first instead of last. Here's the updated example: http://jsfiddle.net/WDrep/6/

I was hoping to use the mapping plugin once on the data received from the server and not on each property individually. This normally works fine, but seems to create problems using the mapping and sorting plugins together.

Thanks again,
Bill

[rniemeyer]

@wjbryant I'll see if I can take a closer look when I get a chance. It appears that it is related to the mapping plugin.

If you take sortable out of the picture and add an item, then do something like:

   var items = viewModel.data.items,
       item = items()[3];

   items.remove(item);
   items.splice(2, 0, item); 

You will see the same behavior.

[wjbryant]

@rniemeyer Thanks for the insight. I guess it's a mapping bug then. You don't even have to remove the item, just using splice to insert any item but the last one has the same effect. Here is an updated and simplified example that I think better demonstrates this: http://jsfiddle.net/WDrep/9/

[rniemeyer]

I think that the best course of action is to open an issue with the mapping plugin. If it turns out that there is something that this plugin can do to help compensate for it, then I would be happy to look at including some changes for it.

[wjbryant]

This is the related knockout-mapping issue: SteveSanderson/knockout.mapping#74

[wjbryant]

The solution from the knockout-mapping issue was to use the create callback to keep everything in sync. I'm not sure why it makes a difference, but it fixes the problem.

Here is an example of this working with the sortable plugin: http://jsfiddle.net/WDrep/11/