Given a class property, you can specify a different access level by prefixing the property declaration with the access modifier followed by get or set between parenthesis. For example, a class property with a public getter and a private setter will be declared as:

private(set) public var readonlyProperty: Int

Suggested reading: Getters and Setters

Martin’s considerations about accessibility level are still valid – i.e. there’s no protected modifier, internal restricts access to the module only, private to the current file only, and public with no restrictions.

Swift 3 notes

2 new access modifiers, fileprivate and open have been added to the language, while private and public have been slightly modified:

• open applies to class and class members only: it’s used to allow a class to be subclassed or a member to be overridden outside of the module where they are defined. public instead makes the class or the member publicly accessible, but not inheritable or overridable

• private now makes a member visible and accessible from the enclosing declaration only, whereas fileprivate to the entire file where it is contained

More details here.