Protocols Extensions | Advanced Swift | Iosdevelopment Tutorial

Introduction to Protocols

Protocols are a powerful feature in Swift that allow you to define blueprints of methods, properties, and other requirements. A protocol can then be adopted by a class, structure, or enumeration to provide an actual implementation of those requirements.

Defining a Protocol

To define a protocol in Swift, use the protocol keyword followed by the protocol's name and a set of requirements enclosed in curly braces.

protocol Describable {
    var description: String { get }
    func describe() -> String
}

Adopting a Protocol

To adopt a protocol, a class, structure, or enumeration must conform to the protocol's requirements by providing implementations for all of the properties and methods specified in the protocol.

struct Car: Describable {
    var description: String {
        return "A car with \(numberOfDoors) doors."
    }
    
    var numberOfDoors: Int
    
    func describe() -> String {
        return description
    }
}

Protocol Inheritance

Protocols can inherit from other protocols. A protocol that inherits from another protocol must meet all the requirements of the inherited protocol as well as its own additional requirements.

protocol Named {
    var name: String { get }
}

protocol Person: Named {
    var age: Int { get }
}

Protocol Extensions

Protocol extensions allow you to provide default implementations for the methods and properties defined in a protocol. This means that any type that adopts the protocol will automatically get these default implementations.

extension Describable {
    func describe() -> String {
        return description
    }
}

Protocol-Oriented Programming

Protocol-oriented programming is a paradigm that emphasizes the use of protocols and protocol extensions to write flexible and reusable code. It encourages designing systems based on behaviors defined by protocols rather than inheritance.

protocol Flyable {
    func fly()
}

extension Flyable {
    func fly() {
        print("Flying")
    }
}

struct Bird: Flyable {}
let bird = Bird()
bird.fly() // Output: Flying

Conclusion

Protocols and extensions are fundamental features of Swift that enable you to write clean, modular, and reusable code. By defining clear contracts with protocols and providing default implementations with extensions, you can build robust and flexible applications.

Advanced Swift: Protocols and Extensions