Kartik Select 2 - Programatically changing multiple - php

Question

I have a yii2 activeform where the functionality of the form can change based on other things within the form. So, I have a clubs field, that can be multiple in some instances but not multiple in others.
<?= $form->field($model, 'clubs')->widget(\kartik\widgets\Select2::classname(), [
'data' => $club_data,
'hideSearch' => false,
'options' => ['placeholder' => 'Add Club(s)'],
'pluginOptions' => [
'allowClear' => true,
'multiple' => true,
'minimumInputLength' => 3,
'ajax' => [
'url' => 'web/index.php?r=clubs/clubslist',
'dataType' => 'json',
'data' => new JsExpression('function(params) { return {q:params.term}; }'),
],
],
])->label('Club(s)'); ?>
I need to programmatically change the multiple pluginOption to true and false. This should be when the user goes into the form but also immediately when a dropdown is changed on the form. I can do it when the user initially goes into the form but not immediately when another dropdown is changed.
I've made separate fields, one actually linked to a field in the database and another not, this kind of works but it's far from elegant!
I've looked in both the kartik select2 documentation and the standard jquery select2 documentation and I can't spot anything. Any help or pointers would be much appreciated.

Answer 1

Reference
I was working on a Yii2-formwizard plugin a few months back where I had a situation of providing tabular functionality and cloning the fields really became the pain in the ass when it came to using 3rd party plugins like Select2 and Datepicker and I figured out the following code along with a lot of other (as the other part isn't relevant to your problem so not adding it).
Approach to the problem
The way Kartik-select2 works it stores the select2 plugin-specific options in the data-krajee-select2 attribute of the element you are using the select2 on.
And the theme or say the Kartik's plugin-specific options like theme and others are saved in the variable whose name is saved in the data-s2-options attribute. You can look for both of them in view-source of the page where you are using it.
Solution
So what you need to do is to
Steps
Get the applied options
Add/Update the option
Apply back the options
As you just added a single field and not the other one on who's selection it would change, I would demonstrate an example where you can change the behavior of the select2 from multiple to single using 2 different buttons, clicking on the relevant button the select2 will work accordingly. You can adjust the javascript code where ever you want to.
But before I add any code you need to fix one thing, you don't need the main data option when you are using the ajax option inside the plugin options. In other words, it does not have any effect on your select2 and is adding page load time only you should remove it.
You select2 should look like below, I added id to the options of the select2 for the example you can change it to the active form formatted name like model-field_name format if you like, but don't forget to change the id in the javascript code too
<?php echo $form->field($model, 'clubs')->widget(\kartik\widgets\Select2::classname(), [
'hideSearch' => false,
'options' => ['placeholder' => 'Add Club(s)','id'=>'clubs'],
'pluginOptions' => [
'allowClear' => true,
'multiple' => true,
'minimumInputLength' => 3,
'ajax' => [
'url' => 'web/index.php?r=clubs/clubslist',
'dataType' => 'json',
'data' => new JsExpression('function(params) { return {q:params.term}; }')
]
]
])->label('Club(s)');?>
Add the following buttons on your page
echo Html::button('multiple', ['class' => 'btn btn-info', 'id' => 'multi']);
echo Html::button('single', ['class' => 'btn btn-info', 'id' => 'single']);
And now the magic thing, add it on the top of your view
$js = <<<JS
var element=$("#clubs");
$('#multi').on('click',function(e){
//reset select2 values if previously selected
element.val(null).trigger('change');
//get plugin options
let dataSelect = eval(element.data('krajee-select2'));
//get kartik-select2 options
let krajeeOptions = element.data('s2-options');
//add your options
dataSelect.multiple=true;
//apply select2 options and load select2 again
$.when(element.select2(dataSelect)).done(initS2Loading("clubs", krajeeOptions));
});
$('#single').on('click',function(e){
element.val(null).trigger('change');
let dataSelect = eval(element.data('krajee-select2'));
let krajeeOptions = element.data('s2-options');
dataSelect.multiple=false;
$.when(element.select2(dataSelect)).done(initS2Loading("clubs", krajeeOptions));
});
JS;
$this->registerJs($js, \yii\web\View::POS_READY);
Now if your select2 is working correctly click on the multiple button and you will see the multiple selections are enabled for the select2 and when clicked on the single button.
Hope it helps.