The 5 access control keywords.

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open class Book { //An “open” class allows subclassing within a context outside of the defining module
    private var name: String //Restricts access to enclosing declaration. Extensions in same class file will be able to access.
    public var isbn: UUID //Does not restrict access.
    fileprivate var genre: String //Restricts access outside of the defining *file*. Classes within the same file will be able to access.
    internal var length: Int //Restrict access outside of the defining *module*.
}

Protected does not exist because:

• It is ambiguous as to whether an extension should be able to access it
• Subclass methods could expose it anyway

All vars/classes/types/entities have a access level of internal by default.

Modifiers:

• If you give something the @testable attribute, it will be accessible by the testing classes, but maintain status as internal/private otherwise.
• You can define access control to an entire class/struct. This will also carry through for all it’s members (properties, methods, initializers, and subscripts)
• If you create a tuple out of two differently access controlled types, it will assume the most restrictive one.
• A function will be as restrictive as it’s parameters or return types are, unless you specify.
• Enum cases cannot have different levels of access, as well as their raw and associated values
• Type aliases can only have the same access level, or a more restrictive one.* this is an oversimplification

Originally published 04/11/2021 @ https://pittcsc.org/ Discord

Published here on 09/08/2022. Blog published date reflects the original date of publication.