In which Symfony event can I have access to which submit button was clicked? - symfony

Question

I would like to do some transformation on the submitted data based on which button on my form was clicked. Here is the scenario:
I have a text field named chain which holds the command chain.
I have a command text field that holds the last command.
I have two buttons on the form: Send and Send chain.
When Send is clicked, chain is set to command, erasing whatever was in it before. When Send chain is clicked, however, the contents of command are added to the end of chain after a delimiter, effectively creating a chain of commands.
I need to be able to check to see which of these two buttons was clicked so that I can set chain to the appropriate value.
Why am I not doing this in the controller? The problem is that I need to modify the value of chain. Since I cannot modify the values of an already-submitted form, I need to do this in an event, I assume. As I mentioned above, I need chain to either be equal to command, or chain + [delimiter] + command.

Answer 1

If I understood you correctly, you don't need an event at all. There is a built in method isClicked() since #2.3. Example from documentation:
if ($form->isValid()) {
// ... do something
// the save_and_add button was clicked
if ($form->get('save_and_add')->isClicked()) {
// probably redirect to the add page again
}
// redirect to the show page for the just submitted item
}
Link to chapter.
Update
Normally, the code I showed can be used in event - FormEvents::POST_SUBMIT to be precise, but as you already pointed out, you can not modify form data after submission. To be honest I can't come up with perfectly working example, so I will share an idea hoping it will lead to something, or at least until someone else suggest something else.
How about you add a hidden non mapped field to your form. Then (assuming you are allowed to use javascript in your form) you can attach event listener on when form is submitted and based on which button was clicked you can populate that hidden field with specific value. After that you can add event listener to your FormType and read the value of this hidden field, using FormEvents::POST_SET_DATA.
I am sorry I can not be more helpful as of now. If I came up with something I will edit my post.

Answer 2

Here is what I needed to do:
I couldn't use the POST_submit event because I couldn't transform the data after submission.
The isClicked() of both buttons returned false in other events, because the form hadn't been submitted yet.
The solution is something like this:
$data = $event->getData();
if (isset($data['send']) {
// transform the values here
}
In other words, the only way to check if a particular button was clicked is to check to see if its name exists as an index in the array returned by $event->getData().