How do I check the value of a field if its empty?

Question

Is there a way to check, in a preprocess function, if the value of a field is empty?

I'm getting the following error.

Call to a member function isEmpty()

function iom_preprocess_block__twitterfeed(&$variables) {
  // Get the twitter_username field from node.
  $twitterUsername = \Drupal::routeMatch()
    ->getParameter('node')
    ->get('field_twitter_username')
    ->value; 

  if ($twitterUsername->isEmpty()) {
    dump("Empty");
  }
  else {
    dump("Not Empty");
  }
}

Answer 1

@vinhd proposition is correct, by the way you can also use the isEmpty() method from the field list interface. It can be more adapted for complex field types.

if($node->hasField('field_your_field') && !$node->get('field_your_field')->isEmpty(){

}

Answer 2

None of the other answers is fully correct, each one will only work in some cases. Before calling an object method, you have to check
- if the object exists,
- if the object is of the right type
- and if the object has that specific method/field.

The following code might look like a bit of an overkill, but it is the most bulletproof solution I've found so far. Everything I'm checking in there is based on a real word error I've had in my own projects:

function MYMODULE_preprocess_MYHOOK(&$variables) {

  $route = \Drupal::routeMatch();

  //special case node preview: has no node object, but a node_preview
  if ($route->getRouteName() == 'entity.node.preview') {
    $node = $route->getParameter('node_preview');
  }
  // this is the default case
  else {
    $node = $route->getParameter('node');
  }

  //$node can be either a node object (most of the times)
  //or an integer (on some admin routes)
  if (is_numeric($node)) {
    $node = \Drupal\node\Entity\Node::load($node);
  }

  // this if-statement is the important part that prevents the error messages
  if ($node instanceof \Drupal\node\NodeInterface && $node->hasField('field_MYFIELD')) {
    // no you can savely do whatever you want with field_MYFIELD
    $myVar = $node->get('field_MYFIELD')->value;
    $isEmpty = $node->get('field_MYFIELD')->isEmpty();
  }   
}

Answer 3

You can try code:

check has field:

$node = \Drupal::routeMatch()->getParameter('node');
if($node->hasField('field_twitter_username')){
  //todo code
}

check empty value

$field_value = $node->field_twitter_username->getValue()
if(!empty($field_value)){
  //todo code
}