CoreData Set Utils

SetUtils.swift

/// Some extensions with overloaded operators for easily adding and removing
/// objects to sets when working with CoreData

import Foundation
import CoreData

protocol ManagedSet {
    var allObjects: [AnyObject] { get }
    init( array: [AnyObject] )
}

extension NSOrderedSet : ManagedSet {
    var allObjects: [AnyObject] { return self.array }
}

extension NSSet : ManagedSet {}

func += <T: ManagedSet>(inout lhs: T, rhs: NSManagedObject) -> T {
    var array = lhs.allObjects as? [NSManagedObject] ?? [NSManagedObject]()
    array.append( rhs )
    lhs = T(array: array)
    return lhs
}

func -= <T: ManagedSet>(inout lhs: T, rhs: NSManagedObject) -> T {
    var array = lhs.allObjects as? [NSManagedObject] ?? [NSManagedObject]()
    array = array.filter { $0 != rhs }
    lhs = T(array: array)
    return lhs
}

func += <T: ManagedSet>(inout lhs: T, rhs: [NSManagedObject]) -> T {
    var array = lhs.allObjects as! [NSManagedObject]
    array = array + rhs
    lhs = T(array: array)
    return lhs
}

func -= <T: ManagedSet>(inout lhs: T, rhs: [NSManagedObject]) -> T {
    var array = lhs.allObjects as! [NSManagedObject]
    array = array.filter { !rhs.contains( $0 ) }
    lhs = T(array: array)
    return lhs
}