[Sort] Adjust sort interface to handle swapping out MatSort

[jscharett]

Bug, feature request, or proposal:

It would be nice to be able to sort on multiple columns.

What is the expected behavior?

The user can sort the grid with multiple columns at a time

What is the current behavior?

The user can sort the grid with a single column

What is the use-case or motivation for changing an existing behavior?

The app I'm working on has a requirement for multi-column sort. I've used other, non-angular, grids in the past and they have supported this.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Angular 4.3.6
Material 2.0.0-beta.10
Typescript 2.5.2

[jelbourn]

There's should actually be nothing stopping one from doing multi-column sorting; you would just need to swap out the current mdSort directive (which holds the sort state) with a variant that has the state for multiple columns.

[jscharett]

Ah, good to know. Still getting familiar with Angular. Thanks

[timwright35]

@jscharett I was just thinking this would be nice myself, I will have to look into how mdSort runs etc it seems.

[prabhat112]

anyone has an example or a plunker implementation of the above suggestion?

[willshowell]

@jelbourn I gave it a shot by providing a MultiSort directive that extends MatSort and uses a collection of active MatSortables instead of a single one.

However, this method in MatSortHeader, which controls whether a sort header is visible, requires a reimplementation of the header.

https://github.com/angular/material2/blob/9b0771286aa867ca111987e5d8232137d6a45d33/src/lib/sort/sort-header.ts#L143-L147

AFAIK it is not currently possible to extend a component while inheriting the decorator, so a reimplementation of MatSortHeader has to also reimplement the template, styles, animations, etc.

If I'm not missing something, this is quite a bit more involved than creating a MatSort variant.

[jelbourn]

@willshowell thanks for giving that a try

@andrewseguin we need to change the matSort/sort-header to each conform to an interface that would allow for different sorting semantics

[Kulikovpavel]

When this feature will be ready and available?
approximately

[dnemoga]

Any updates?

[fxck]

Is this planned anytime soon? Looks like there is nothing table related in the plan anymore..

[relair]

I am thinking about changing this myself, since I need multi column sorting and this doesn't seem to be addressed any time soon. So the problem right now is interface which is essentially a value of sort.active and _sort.direction which are just strings.
I am thinking of either them being potentially an array (and add a check for it) - otherwise use current logic for backwards compatibility or alternatively have some new property with collection of tuples with id and direction and then have it work next to old properties which may become obsolete by this point.