sort pagearray on calculated values

[Spica]

I have a pagearray, each page has a location. I calculate the distance to a given location for each page's location. How would I best organize a sort of the pagearray on the distance. The distance is not a field of the pages but calculated. Hope I am clear enough.

[LostKobrakai]

You can sort by runtime fields as well. You'd just need to make sure to populate it before sorting.

[kongondo]

That would require an in-memory sort. One way to do it (as we wait for @LostKobrakai's better answer  )....

Create and populate a property 'distance' on the fly for each page in the PageArray then sort the array by that property. An example:

// get a PageArray
$res = $pages->find('template=basic-page, limit=15');	

// assign distances to a property 'distance' created on the fly
foreach ($res as $r) {
    $r->distance = rand(5, 100);// we assign some random distance just for testing
}

// testing output
$out = '';

// sort
#$res->sort('distance');// sort ascending
$res->sort('-distance');// sort descending

// confirm sorting worked
$out .= '<ol>';
foreach ($res as $r) {
    $out .= '<li>' . $r->title . ': distance - ' . $r->distance . ' Miles</li>';
}
$out .= '</ol>';

// it works!
echo $out;

You should get results similar to this:

1. X-Small: distance - 84 Miles
2. XX-Large: distance - 84 Miles
3. Small: distance - 77 Miles
4. US Open: distance - 75 Miles
5. About Us: distance - 74 Miles
6. Our Achievements: distance - 69 Miles
7. Key Staff: distance - 65 Miles
8. Who We Are: distance - 57 Miles
9. X-Large: distance - 57 Miles
10. Senior Management: distance - 51 Miles
11. Medium: distance - 41 Miles
12. Sizes: distance - 39 Miles
13. Colours: distance - 25 Miles
14. Large: distance - 10 Miles
15. What We Do: distance - 9 Miles

Useful reading: PageArray

Edited April 12, 2016 by kongondo
Edit: slow again! I told you he'd give you a great answer :-)

[Spica]

Ah, thanks, kongondo,

that was the missing link / information for me.

I now just wonder about the best sort strategie. I have different sort options beside the distance to sort the pagearray. All given by a users selection. So all other sort options are executed within the selector in $pages->find. Distance cannot be sorted within find. Should I mix find(sort=) with $res->sort() routines or do a routine just with $res->sort() for all sort options. Are there any reasons to prefere a sorting within find() over sort()?

[LostKobrakai]

If you need to use pagination (limit=XX) for the resulted pages you'd need to resort to something like this: https://github.com/ryancramerdesign/ProcessWire/issues/556

If you're not using limit in your selector I'd suggest using sort in the $pages->find() selector if possible and fall back to runtime sorting only if needed.

Edit: The difference between find() and sort() is, that find() will sort results in mysql and therefore (in conjuction with limit) will only load actually displayed pages, whereas sort() does only sort pages in php (loaded to memory), which might draw a lot of performance if done on a large set of pages.

[Spica]

Good Point, LostKobrakai, actually I need a pagination. So sort() seems not to be the right way. Will check your link, at first glance it seems more compicated than expected.

[LostKobrakai]

That's mostly owing the fact that the distance calculation must be done in sql syntax.

[Spica]

I found an fork of FieldtypeMapMarker I already worked with that already does the sorting in the sql query. Think that could fit my needs.