Insert a value to $form_state

Question

    function form_example_form($form, &$form_state) {
      $form_state ['store_value'] =1;
      $form['submit_button'] = array(
        '#type' => 'submit',
        '#value' => t('Click Here!'),
      );


  return $form;
}

How to do this in drupal 8

Answer 1

Insert the the value in $form_state:

$form_state->set('store_value', 1);

And then later for example in submitForm():

$value = $form_state->get('store_value');

Don't use getValue() or setValue(), because this is for submitted values.

If you are migrating more forms from D7 to D8, use this as reference:

$form_state is now a classed object

Answer 2

$form_state is a instance of FormState object, you need use setValue($key, $value) method to store values on it.

Check the docs for additional info.

From docs:

Parameters

string|array $key: Values are stored as a multi-dimensional associative array. If $key is a string, it will use $values[$key] = $value. If $key is an array, each element of the array will be used as a nested key. If $key = array('foo', 'bar') it will use $values['foo']['bar'] = $value.

mixed $value: The value to set.