Access Control Examples

####Examples from "Swift 2 to 3" by Erica Sadun
Available from iTunes and LeanPub

Basic Control Keywords

// Default is internal
struct MyType {
    let member: String = "Member" // default is internal
    fileprivate let filemember: String = "FileMember"
    private let privatemember: String = "PrivateMember"
    internal let internalmember: String = "InternalMember"
    public let publicmember: String = "PublicMember"
    public init() {}
}

private struct MyPrivateType {
    let member: String = "Member" // default is internal
    fileprivate let filemember: String = "FileMember"
    private let privatemember: String = "PrivateMember"
    internal let internalmember: String = "InternalMember"
    public let publicmember: String = "PublicMember"
    public init() {}
}

fileprivate struct MyFilePrivateType {
    let member: String = "Member" // default is internal
    fileprivate let filemember: String = "FileMember"
    private let privatemember: String = "PrivateMember"
    internal let internalmember: String = "InternalMember"
    public let publicmember: String = "PublicMember"
    public init() {}
}

internal struct MyInternalType {
    let member: String = "Member" // default is internal
    fileprivate let filemember: String = "FileMember"
    private let privatemember: String = "PrivateMember"
    internal let internalmember: String = "InternalMember"
    public let publicmember: String = "PublicMember"
    public init() {}
}

public struct MyPublicType {
    let member: String = "Member" // default is internal
    fileprivate let filemember: String = "FileMember"
    private let privatemember: String = "PrivateMember"
    internal let internalmember: String = "InternalMember"
    public let publicmember: String = "PublicMember"
    public init() {}
}

Type	Scope	Visibility	Outside of Type	In Type Extension
All five types	Same file	Can create instances	`privatemember`: inaccessible due to 'private' protection level	`privatemember` is unresolved identifier
MyType, MyInternalType, and MyPublicType	Same module, different file	Can create instances	`privatemember` and `filemember`: inaccessible due to 'private' protection level	`privatemember` and `privatemember` are unresolved identifiers
MyFilePrivateType and MyFilePrivateType	Same module, different file	Undeclared types	N/A	N/A
MyPublicType	External to module	Can create instances	Can access `publicmember` but no other members	`publicmember` is visible
MyFilePrivateType, MyPrivateType, MyType, MyInternalType	External to module	Undeclared types	N/A	N/A

Open vs Public Classes and Members

public class PublicClass {
    public let propertyPublic = "PublicMember"
    public func actionPublic() {}
    open let propertyOpen = "PublicMember"
    open func actionOpen() {}
}

open class OpenClass {
    public let propertyPublic = "PublicMember"
    public func actionPublic() {}
    open let propertyOpen = "PublicMember"
    open func actionOpen() {}
}

Type	Scope	Actions
OpenClass and Public Class	Same Module, Any File	Can subclass and override methods
OpenClass	External to Module	Can subclass and override open methods. Cannot override non-open methods outside defining module
Public Class	External to Module	Cannot subclass or override from non-open class outside defining module