Understanding Protocol-oriented programming

Protocol-oriented programming is a programming paradigm in which the focus is on defining and using protocols to solve problems. In protocol-oriented programming, protocols are used to define the behavior and properties that a conforming type must have. This allows you to define the interface for a type without specifying its implementation, which makes it easier to create and use abstractions in your code.

In Swift, you can use protocol-oriented programming techniques to write flexible and extensible code. Here is an example of protocol-oriented programming in Swift:

protocol Shape {
    var area: Double { get }
    func draw()
}

struct Circle: Shape {
    let radius: Double
    var area: Double {
        return Double.pi * radius * radius
    }

    func draw() {
        // Draw a circle
    }
}

struct Square: Shape {
    let side: Double
    var area: Double {
        return side * side
    }

    func draw() {
        // Draw a square
    }
}

let circle = Circle(radius: 10)
let square = Square(side: 10)

let shapes: [Shape] = [circle, square]

for shape in shapes {
    print(shape.area)
    shape.draw()
}

In this example, a Shape protocol is defined that has an area property and a draw() method. The Circle and Square structs conform to the Shape protocol and provide their own implementations of the area property and the draw() method.

The Circle struct has a radius property and calculates the area of the circle using the formula for the area of a circle. The Square struct has a side property and calculates the area of the square using the formula for the area of a square.

The Shape protocol allows the Circle and Square structs to be treated as if they are the same type. This is demonstrated by the shapes array, which is declared to be an array of Shape values and contains both a Circle instance and a Square instance.

This example shows how you can use protocol-oriented programming in Swift to define and use protocols to create abstractions in your code. By defining a protocol that specifies the behavior and properties that a conforming type must have, you can create a type-agnostic interface that allows you to treat different types in a consistent way.