What is the difference between a protocol and an interface in programming?

In programming, protocols and interfaces are often used to describe a set of methods that a class or structure must implement, but there are differences between them, especially in the context of iOS and Swift.

• Protocol — this is a concept from Swift and Objective-C that defines a set of requirements (methods, properties) that a class, structure, or enumeration must implement. Protocols can contain required and optional methods, as well as properties. They allow for flexible and extensible architectures, support multiple inheritance through composition.

• Interface — a term more common in other programming languages (e.g., Java, C#). An interface is a contract that defines a set of methods without implementation that a class must implement. In Swift, the equivalent of an interface is a protocol.

Thus, in the context of iOS and Swift, protocols serve the role of interfaces but have additional capabilities, such as protocol extensions (default implementation) and the ability to be implemented not only by classes but also by structures and enumerations.