Processing not working when JSON has only one row with a null value

boni

Here's the situation: I have a table that displays assignments, but the end-date of the assignment can be null.
It works fine when there are assignments with end-dates, however as soon as my data only contains a single record, and the end-date is null, it doesn't work anymore.
I'm using sAjaxSource to get the JSON data and when that happens I get the following JS-Error:
[quote]"Uncaught TypeError: Cannot read property 'length' of null" in jquery.dataTables.js:2649[/quote]

Here is my Table:
[code]projectMemberTable = $('#project_member_entries').dataTable({
"bProcessing" : true,
"sAjaxDataProp" : "data",
"sAjaxSource" : baseURL + memberURL + '/all',
"aoColumns" : [ {
"mData" : "id",
"bSearchable" : false,
"bVisible" : false
}, {
"mData" : "user",
"bSearchable" : false,
"bVisible" : false
}, {
"mData" : "userName"
}, {
"mData" : "role",
"mRender" : function(data, type, full) {
return projectRoles[data];
}
}, {
"mData" : "startDate",
"mRender" : dataTableDate
}, {
"mData" : "endDate",
"mRender" : dataTableDate
}, {
"mData" : null,
"bSearchable" : false,
"bSortable" : false,
"fnRender" : function(oObj) {
return '';
}
}, {
"mData" : null,
"bSearchable" : false,
"bSortable" : false,
"fnRender" : function(oObj) {
return '';
}
} ]
});[/code]

And here is the exact JSON that causes this problem:
[code]{
"data" : [ {
"id" : 128,
"user" : 5,
"project" : 127,
"startDate" : "2012-12-22T15:13",
"endDate" : null,
"userName" : "Benjamin Boss",
"role" : "LEADER"
} ]
}[/code]

I've tried to debug it, but I can't seem to find the reason. :/

allan

The question comes down to, how do you display the absence of data (i.e. null)? An empty cell (i.e an empty string) if you take the Oracle method. Or a cell with `No data` in it? DataTables allows both and more by using the sDefaultContent option - but you need to use this parameter to tell DataTables what to do with null data - it will not just treat it as an empty string (or anything else - it is null, not an empty string!).

Allan

boni

I've tried using sDefaultContent. Does not solve the problem.
It's really weird, because it causes no problems if there are two entries, and the second one contains a null, it works without problems:
[code]{
"data" : [ {
"id" : 5,
"user" : 1,
"project" : 1,
"startDate" : "2013-10-19T08:23",
"endDate" : "2014-10-19T08:23",
"userName" : "Max Mustermann",
"role" : "MEMBER"
}, {
"id" : 4,
"user" : 5,
"project" : 1,
"startDate" : "2011-10-19T08:23",
"endDate" : "2012-12-31T00:00",
"userName" : "Benjamin Boss",
"role" : "LEADER"
}, {
"id" : 141,
"user" : 5,
"project" : 1,
"startDate" : "2012-12-31T00:00",
"endDate" : null,
"userName" : "Benjamin Boss",
"role" : "MEMBER"
} ]
}[/code]

This json correctly displays the 3 rows in the table, while the one in my first post just displays nothing and the datatable is stuck at "Processing". With the 3-entry-json, no javascript-error is thrown. So it seems to me that the handling of null if it's in the first/only row is a problem?

I can change my webservice to return an empty string instead of null for all those instances, shouldn't be a problem. But looks like a bug to me. :)

Merry Christmas and thanks for everything (including the awesome datatable)!

allan

If you could link to a test case showing the error, I'll be able to address the issue if it is a bug, benefiting everyone :-)

However, as you can see in this example I just put together, it should work just fine: http://live.datatables.net/odogus/edit#javascript,html

Allan

boni

Okay, this is really weird. I tried the nightly version instead of the one we were using in the project (1.9.4) and it worked. Then I tried the old one again.. and it still worked. The code is unchanged.

Might be the that it was a problem in combination with the browser cache. It sometimes just refuses to refresh. I can't reproduce the problem right now, so I'll asume it just magically fixed itself over christmas. ;)

Thanks for your help, I'll try to save/create a small testcase if it happens again.

allan

Heh - Merry Christmas ;-)

Allan

boni

It's back again. But this time I managed to get a small test case where it happens! It's a bit different this time, but it seems to be reproducable.

The error: Uncaught TypeError: Cannot read property 'length' of null
What's happening: Processing... is just shown forever
What data: The data is received via ajax and nested in a json object. But the data itself is null.

Excuse the terrible coding, but I just tried to get a quick and dirty test case together and had no proper way of uploading stuff. I used your example from above as base. :)

Here is the bad test case:
Website: http://boni.bbgen.net/dt.html
Data: http://boni.bbgen.net/empty.json

Here is a good test case, to show you that it works with correct data:
Website: http://boni.bbgen.net/dt2.html
Data: http://boni.bbgen.net/valid.json

Please tell me if that helps. :)

boni

Did this go down in the flood of new discussions on the front page? :/

allan

[code]
{
"data": null
}
[/code]

Change that to an empty array rather than `null` and it should work okay :-). Your JSON there is valid, but DataTables doesn't know what to do with it. Possibly it should handle that, and I'll look into that, but for the moment, just return an empty array when you've got no data. I'd say that's a more accurate representation of the data (or lack of it) anyway.

Allan

boni

Will do, I just figured the fix would be the same as for the original problem I had (with the null as data for some contained object). This just was the only way I managed to reproduce it. Probably was a cache error after all. ;)