API

Get a Folder

<?php
use Wicked_Folders\Folder_Factory;

$folder_id = 1;
$post_type = 'attachment';
$folder    = Folder_Factory::get_folder( $folder_id, $post_type );

$folder->fetch();

Get Folders

<?php
use Wicked_Folders\Folder_Collection;

$post_type  = 'attachment';
$folders    = new Folder_Collection( $post_type );

Get Posts by Folder

<?php
use Wicked_Folders\Folder_Factory;

$folder_id = 1;
$post_type = 'attachment';
$folder    = Folder_Factory::get_folder( $folder_id, $post_type );
$posts 	   = $folder->fetch_posts();

Create a Folder

<?php
use Wicked_Folders\Term_Folder;

$folder 			= new Term_Folder();
$folder->name 		= 'Sample Folder';
$folder->post_type 	= 'attachment';
$folder->parent 	= 1; // Optional parent folder ID

$folder->save();

Assign a Post to a Folder

<?php
$post_id 	= 1;
$folder_id 	= 1;

Wicked_Folders::move_object( 'post', $post_id, $folder_id );

REST API

Please see wp-content/plugins/wicked-folders-pro/core/classes/rest-api/v1/class-folder-api.php for REST API functions.