Swift 4 Protocol-Oriented Programming - Third Edition

Access controls

Access controls allow us to restrict the access to, and visibility of, parts of our code. This allows us to hide implementation details and only expose the interfaces we want the external code to access. We can assign specific access levels to both classes and structures. We can also assign specific access levels to properties, methods, and initializers that belong to our classes and structures.

In Swift, there are five access levels:

• Open: This is the most visible access control level. It allows us to use a property, method, class, and so on anywhere we want to import the module. Basically, anything can use an item that has an access control level set to open. Anything that is marked open can be subclassed or overridded ...