Drupal 8 field wrangling

d8-fieldapi-tricks.txt

// Check whether a node's bundle has a particular field
if ($node->hasField('field_might_be_missing')) { ... }

// Check field-type-specific empty/not empty logic
if ($node->field_name->isEmpty()) { ... }

// Iterate over individual instances in a field. field_name isn't an actual
// array, but a special iteratable class, so it won't die if the field is empty.
foreach ($node->field_name as $delta => $field_instance) { ... }

// Return an array containing the raw property values for the field.
// If a delta is specified, only that field delta's values are returned.
$node->field_name->getValue();             // [ 0 => ['value' => 'foo', 'format' => 'basic_html']]
$node->field_name[0]->getValue();          // ['value' => 'foo', 'format' => 'basic_html']

// Retrieve one particular property from a field instance.
// If no delta is specified for a multi-value field, delta 0 is assumed.
$node->field_name->format;        // 'basic_html'
$node->field_name[0]->format;     // 'basic_html'

// Working with Entity Reference fields
$node->field_related->target_id;             // Raw entity ID
$node->field_related->entity;                // Fully loaded entity
$node->field_related->entity->field_remote;  // Field instance on the loaded entity

// Generate a render array for a given field. If no display mode is
// passed in, 'default' is assumed.
$node->field_name->view('default');

// Fancier tricks! In a preprocess hook, pull a field from a referenced node
$variables['content']['field_remote'] = $node->field_related->entity->field_remote->view('default'));