Support sorting by nested properties

[ohadschn]

The current sorting code starts with the following:

rows.sort (a,b) =>
        aVal = ko.utils.unwrapObservable a[@sortField()]
        bVal = ko.utils.unwrapObservable b[@sortField()]

As such, only flat properties of the row object can be used for sorting.
For example, suppose my row looks like this:

{
    foo:
    {
        bar: "foobar"
    }
}

It would have been nice to be able to sort by foo.bar

[cmbankester]

Typically, the filter is bound directly to a text/search input and aren't often accessed programmatically (at least that's the way we usually use it). I can see the functionality you're describing being mighty useful, though. If you want to submit a PR, I'd be glad to merge it in. Otherwise, I'll get to this one when I have some free time on my hands.

[ohadschn]

Hi @cmbankester,

I was referring to the sorting feature (not filtering), which is typically bound to a property on the row. For example if we take demo.html, a row looks like this:

function City(view, row) {
          this.view = view;
          this.population = ko.observable(row.population);
          this.countryName = row.country_name;
          this.cityName = row.city_name;
        }

And in the HTML you have a binding such as:

<th data-bind="click: toggleSort('cityName')" class="sortable">

What I'm saying is that if cityName were a complex object, say:

cityName = 
{
   shortName : "NY",
   fullName: "New York"
}

Then the following would not work presently:

<th data-bind="click: toggleSort('cityName.shortName')" class="sortable">

[ohadschn]

On an unrelated note, I don't want all the issues I've opened to make the wrong impression. I think knockout-datatable is great. I would not have gone to the trouble of going over the sources (learning CoffeeScript and LESS for this purpose alone) and opening all these issues otherwise. I have searched long and hard and I believe this is the best solution of its kind. Kudos!

[cmbankester]

@ohadschn Thanks! I didn't get the wrong impression at all, I am very pleased that these issues have been opened. It's great to see other people getting use out of our open-source products.

One approach to the sort-by-object-attributes situation you've outlined above could be to alias cityName.shortName as cityShortName on your row, making your row look like:

function City(view, row) {
  this.view = view;
  this.population = ko.observable(row.population);
  this.countryName = row.country_name;
  this.cityName = row.city_name;
  this.cityShortName = this.cityName.shortName;
}

with corresponding binding:

<th data-bind="click: toggleSort('cityShortName')" class="sortable">

Would that be acceptable? I don't believe it would be much trouble to add support for sorting by object attributes, I'm just used to flattening my sortable/filterable row attributes.

[ohadschn]

Yes, that's precisely what I did in my case, so for me it was totally acceptable :)

Perhaps there could be some other scenarios where row structure has to be maintained though, or at least easier to keep the way it is (I know I had to go and rename a lot of stuff, which is tiresome in untyped languages like javascript and HTML)