Get Array from Optional NSSet. Especially useful for getting an Array of objects in a Core Data many relationship.

Optional+Extensions.swift

/* 
 * Returns Array from optional NSSet. Returns empty array if NSSet is nil.
 * It's useful for when you want an Array of objects from a Core Data many relationship.
 * 
 * Example usage with managed object `game` with 1-to-many relationship to `Goal` entity: 
 *    let goalArray = game.goals.array(of: Goal.self)
 */

extension Optional where Wrapped == NSSet {
    func array<T: Hashable>(of: T.Type) -> [T] {
        if let set = self as? Set<T> {
            return Array(set)
        }
        return [T]()
    }
}