PostImagesModel.swift

class PostImagesModel {
    enum CellImage {
        case Required, Add, Actual(image: UIImage), Remote(url: NSURL)
    }

    private let maxLimit = 6

    private var items: [CellImage] = []

    func add(image: UIImage) {
        items.append(.Actual(image: image))
    }

    func add(url: NSURL) {
        items.append(.Remote(url: url))
    }

    func remove(index: Int) {
        guard index < items.count else { return }

        items.removeAtIndex(index)
    }

    var toDisplay: [CellImage] {
        get {
            guard !items.isEmpty else {
                return [.Required]
            }

            var toReturn = items

            if items.count < maxLimit {
                toReturn.append(.Add)
            }

            return toReturn
        }
    }
}