Explain the main ideas and approaches of protocol-oriented programming.

Protocol-Oriented Programming (POP) is a paradigm that emphasizes the use of protocols to define interfaces and behaviors rather than inheritance. Main ideas of POP:

• Protocols describe requirements for types — a set of methods, properties, and other requirements that a type must implement.
• Protocol extensions allow adding default implementations, reducing code duplication.
• Types (structs, classes, enums) can conform to multiple protocols, enabling flexibility and composition.
• Avoiding deep inheritance in favor of composition and delegation through protocols.

Example in Swift:

protocol Drawable {
    func draw()
}

extension Drawable {
    func draw() {
        print("Drawing an object")
    }
}

struct Circle: Drawable {}

let circle = Circle()
circle.draw() // Prints: Drawing an object

This approach improves modularity, testability, and extensibility of code, especially useful in iOS development.