Altering (adding) field value when is unknown

Question

I have three content types (A,B,C). A and B have title, author, and field_version (a custom field), while C doesn't have field_version. Let's assume I have a method that gets the version value from a node. (The $node parameter is an entity object.)

function getLatestVersion($node) {
   $version = $node->get('field_version'); //for A, B is OK, but for C - field_version is unknown
}

How can I check the field exists for the node passed as argument without comparing the node type with an hard-coded list?

Answer 1

For nodes, like for every content entity, you can use code similar to the following one to check if a Field API field(^*) exists.

if ($node->hasField('field_version')) {
  // The node has that field; access it with $node->hasField('field_version').
}

A more generic code that would work for either Field API fields or non-field properties would be similar to the following one.

if (isset($node->field_version)) {
  // The node has that field/property; access it with $node->field_version.
}

^* I am using the terminology used in a comment for code in ContentEntityBase::__isset().

// "Official" Field API fields are always set. For non-field properties,
// check the internal values.
return $this->hasField($name) ? TRUE : isset($this->values[$name]);