Replies

• allan Posts: 61,972Questions: 1Answers: 10,160 Site admin

  May 2014

  What a brilliant question - thank you for this!

  So the way I would approach this is to break it into two individual filters. The way DataTables operates the custom filters is that each one is applied to all rows before the next filter is applied, itself to all rows, etc.

  So the first filter would be the age check and that's fairly trivial:

  $.fn.dataTable.ext.search.push(
    function( settings, data, dataIndex ) {
      return data[3] < 40 ? false : true;
    }
  );
  

  Then we want to do do the unique filter. That can be done by keeping a cache of the cities we have seen before and using the DataTables draw counter to know if we should reset that filter or not. I've done that like this:

  var _uniqueFilter = [];
  var _lastDraw = null;
  
  $.fn.dataTable.ext.search.push(
    function( settings, data, dataIndex ) {
      // If starting a new order, reset the filter
      if ( _lastDraw !== settings.iDraw ) {
        _uniqueFilter = [];
        _lastDraw = settings.iDraw;
      }
      
      // Check if there is already a matching city
      if ( _uniqueFilter.indexOf( data[2] ) !== -1 ) {
        return false;
      }
  
      _uniqueFilter.push( data[2] );
      return true;
    }
  );
  

  Working example: http://live.datatables.net/sisudix/2/edit

  if the 'order' variable is changed to [5, 'desc'], I get the result I'm looking forward, but ordered in the wrong way.

  This is due to a quirk of how the sorting is applied. DataTables is going through the display rows in reverse... It does this simply because it makes removing elements from the array slightly easier.

  I've never specified in the documentation the ordering of how the filters work (when working with custom filters they've always been individual row filters, no interdependency), so I'm inclined to change this as it makes far more sense to loop through the array forwards.

  Let me look into that and I'll post back.

  Regards,
  Allan
• Eensim Posts: 3Questions: 0Answers: 0

  May 2014

  Hi Allan,

  Thanks for your support! Your code looks a lot cleaner than mine, so that's already a big improvement :)

  Just a quick note (you're probably aware of this, but just to be safe!):
  The working example that you posted does not return the person with the lowest salary per city, who is at least 40.

  It's funny that you mentioned this fact about datatables, because that's exactly what I was thinking 'it looks like the results are ordered in reverse'! (i.e. I was getting the highest, instead of the lowest salaries per city etc
  ;)
• allan Posts: 61,972Questions: 1Answers: 10,160 Site admin

  May 2014

  I've just committed the required change and will ensure that this is documented and added as part of the test suite while I'm updating them for 1.10 (the developer documentation is in progress for 1.10...!).

  So a slight update to the example: http://live.datatables.net/sisudix/3/edit .

  I've also had it pass in the loop index so the draw counter isn't needed any more.

  Filtering is one area in DataTables I really want to improve, so thanks for your feedback on this!

  Regards,
  Allan
• Eensim Posts: 3Questions: 0Answers: 0

  May 2014

  Brilliant, going to try this out tomorrow and report back!