vialyx

protocol EmailFormType {
    // protocol definition goes here
}

vialyx

protocol Printable {
    // protocol definition goes here
}

protocol Selectable {
    // protocol definition goes here
}

struct EmailItem: Printable, Selectable {
    // structure definition goes here

vialyx

protocol CardType {
    var holderName: String { get set }
    var number: String { get set }
    var expiration: String? { get set }
    var month: String? { get }
    var year: String? { get }
}

vialyx

struct Card: CardType {
    var holderName: String
    var number: String
    var expiration: String?
    var month: String? { return "" }
    var year: String? { return "" }
}

vialyx

protocol Mockable {
    static func mock(_ option: Int) -> Self
}

vialyx

extension Card: Mockable {
    
    static func mock(_ option: Int) -> Card {
        switch option {
        case 1:
            return Card(holderName: "John Malkovich", number: "4111 1111 1111 1111", expiration: "09/12")
        default:
            return Card(holderName: "Mock", number: "0000 0000 0000 0000", expiration: "00/00")
        }
    }

vialyx

protocol CardType {
    var holderName: String { get set }
    var number: String { get set }
    var expiration: String? { get set }
    var month: String? { get }
    var year: String? { get }
}

struct Card: CardType {
    var holderName: String

vialyx

// enable entities to be used within any source file from their defining module, and also in a source file from another module that imports the defining module.
public var publicVariable = 0
// enables entities to be used within any source file from their defining module, but not in any source file outside of that module.
internal let internalConstant = 1
// access restricts the use of an entity to its own defining source file.
fileprivate var fileprivateVariable = 2
// restricts the use of an entity to the enclosing declaration, and to extensions of that declaration that are in the same file.
private let privateConstant = 3

vialyx

class Media {
    var url: String
    
    init(url: String) {
        self.url = url
    }
    
}

class Video: Media {

vialyx

let mediaSet: [Media] = [Video(url: "http://[email protected]", thumb: "http://[email protected]"),
                         Video(url: "http://[email protected]", thumb: "http://[email protected]"),
                         Media(url: "http://[email protected]")]

for media in mediaSet {
    // We don't sure about casting result
    if let video = media as? Video {
        print("Video: \(video)")
    }