Tags via AJAX actionTrigger

Question

I pretty much followed this and the answer there really helped me a lot so far. Currently I'm stuck with either a 500 (Internal Server Error) or a 400 (Bad Request) Error. My craft/storage/runtime/logs/craft.log read the following:

For 400

[error] [exception.Craft\HttpException.400] Craft\HttpException: POST param “title” doesn’t exist. in XXX/craft/app/services/HttpRequestService.php:509
Stack trace:
0 XXX/craft/app/controllers/TagsController.php(235): Craft\HttpRequestService->getRequiredPost('title')
1 XXX/craft/app/framework/web/actions/CInlineAction.php(49): Craft\TagsController->actionCreateTag()
2 XXX/craft/app/framework/web/CController.php(308): CInlineAction->runWithParams(Array)
3 XXX/craft/app/framework/web/CController.php(286): CController->runAction(Object(CInlineAction))
4 XXX/craft/app/framework/web/CController.php(265): CController->runActionWithFilters(Object(CInlineAction), Array)
5 XXX/craft/app/framework/web/CWebApplication.php(282): CController->run('createTag')
6 XXX/craft/app/etc/web/WebApp.php(818): CWebApplication->runController('tags/createTag')
7 XXX/craft/app/etc/web/WebApp.php(288): Craft\WebApp->_processActionRequest()
8 XXXcraft/app/framework/base/CApplication.php(185): Craft\WebApp->processRequest()
9 XXX/craft/app/index.php(62): CApplication->run()
10 XXX/index.php(19): require_once('/var/www/vhosts...')
11 {main}
REQUEST_URI=/actions/tags/createTag
HTTP_REFERER=XXX
---

When I add title: "Tags" to the POST data it results in the 500 with following error:

[error] [system.db.CDbCommand] CDbCommand::execute() failed: SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`craft_`.`craft_tags`, CONSTRAINT `craft_tags_groupId_fk` FOREIGN KEY (`groupId`) REFERENCES `craft_taggroups` (`id`) ON DELETE CASCADE). The SQL statement executed was: INSERT INTO `craft_tags` (`uid`, `groupId`, `id`, `dateUpdated`, `dateCreated`) VALUES (:yp0, :yp1, :yp2, :yp3, :yp4).
2016/11/03 22:16:01 [error] [exception.CDbException] CDbException: CDbCommand failed to execute the SQL statement: SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`craft_`.`craft_tags`, CONSTRAINT `craft_tags_groupId_fk` FOREIGN KEY (`groupId`) REFERENCES `craft_taggroups` (`id`) ON DELETE CASCADE) in XXX/craft/app/framework/db/CDbCommand.php:358
Stack trace:
#0 XXX/craft/app/framework/db/ar/CActiveRecord.php(1081): CDbCommand->execute()
#1 XXX/craft/app/framework/db/ar/CActiveRecord.php(810): CActiveRecord->insert(NULL)
#2 XXX/craft/app/services/TagsService.php(396): CActiveRecord->save(false)
#3 XXX/craft/app/controllers/TagsController.php(237): Craft\TagsService->saveTag(Object(Craft\TagModel))
#4 XXX/craft/app/framework/web/actions/CInlineAction.php(49): Craft\TagsController->actionCreateTag()
#5 XXX/craft/app/framework/web/CController.php(308): CInlineAction->runWithParams(Array)
#6 XXX/craft/app/framework/web/CController.php(286): CController->runAction(Object(CInlineAction))
#7 XXX/craft/app/framework/web/CController.php(265): CController->runActionWithFilters(Object(CInlineAction), Array)
#8 XXX/craft/app/framework/web/CWebApplication.php(282): CController->run('createTag')
#9 XXX/craft/app/etc/web/WebApp.php(818): CWebApplication->runController('tags/createTag')
#10 XXX/craft/app/etc/web/WebApp.php(288): Craft\WebApp->_processActionRequest()
#11 XXX/craft/app/framework/base/CApplication.php(185): Craft\WebApp->processRequest()
#12 XXX/craft/app/index.php(62): CApplication->run()
#13 XXX/index.php(19): require_once('/var/www/vhosts...')
#14 {main}
REQUEST_URI=/actions/tags/createTag
HTTP_REFERER=XXX
---

Any suggestions would be much appreciated. This is the JS code I'm using:

$('#new-tag').click(function() {
    var name = prompt('What’s the new tag name?');
    if (!name) return;
    var data = {
        title: 'tags',
        groupId: 2,
        name: name
    };
    $.post('/actions/tags/createTag', data, function(response) {
        if (response.success) {
            $('<label>' +
            '<input type="checkbox" name="fields[tags][]" value="'+response.id+'" checked="checked"/> ' +
            name +
            '</label>').appendTo($('#tags'));
        }
        else {
            alert('Unable to create that tag.');
        }
    });
});

Answer 1

After some debugging I found, what I did wrong: I had for some reason the wrong groupID (checked that in the backend and DB) as well as title needs to be present in the passed data and is the name of the tag itself.