better post metadata and property getter

includes/transformer/class-base.php

@@ -78,20 +78,39 @@ abstract class Base { // todo renmae to Base_tranformer
 	/**
 	 * Retrieves a post meta field for the configured post.
 	 *
-	 * @param string $key     Optional. The meta key to retrieve. By default,
-	 *                        returns data for all keys. Default empty.
-	 * @param bool   $single  Optional. Whether to return a single value.
-	 *                        This parameter has no effect if `$key` is not specified.
-	 *                        Default false.
+	 * @param string $key     The meta key to retrieve. By default,
+	 *                        returns data for all keys.
+	 * @param bool $single Optional. Whether to return a single value.
+	 *                         This parameter has no effect if `$key` is not specified.
+	 *                         Default false.
+	 * @param mixed $default_value Optional. if the key doesn't exists, it returns the default value.
+	 *                         Default null.
 	 * @return mixed An array of values if `$single` is false.
 	 *               The value of the meta field if `$single` is true.
 	 *               False for an invalid `$post_id` (non-numeric, zero, or negative value).
 	 *               An empty string if a valid but non-existing post ID is passed.
 	 */
-	public function get_post_meta( string $key = '', $single = false, $default = null ) {
-		// todo test what if not present
-		// empty string or empty array, then return default
-		return \get_post_meta( $this->wp_post->ID, $key, $single );
+	public function get_post_meta( $key, $single = false, $default_value = null ) {
+		if ( \metadata_exists( 'post', $this->wp_post->ID, $key ) ) {
+			return \get_post_meta( $this->wp_post->ID, $key, $single );
+		}
+		return $default_value;
+	}
+
+	/**
+	 * Retrieves a post property field for the configured post.
+	 *
+	 * @param string $key     The property key to retrieve. By default,
+	 *                        returns data for all keys.
+	 * @param mixed $default_value Optional. if the key doesn't exists, it returns the default value.
+	 *                         Default null.
+	 * @return mixed The value of the property.
+	 */
+	public function get_post_property( $key, $default_value = null ) {
+		if ( isset( $this->wp_post->$key ) ) {
+			return $this->wp_post->$key;
+		}
+		return $default_value;
 	}
 
 	/**