extentionsExamples.swift

import Foundation

// Extensions
extension Double {
    var squared: Double { return self * self}
}


let sideLength: Double = 12.5
let area = sideLength.squared

//print(area)


struct Car {
    let maker: String
    let model: String
    let year: Int
    
    var fuelLevel: Double {
        willSet {
            precondition(newValue <= 1.0 && newValue >= 0.0, "New value must be between 0 and 1")
        }
    }
}

// Conform protocol
extension Car: CustomStringConvertible {
    var description: String {
        "\(maker) - \(model)"
    }
}

// Initializers
extension Car {
    init(maker: String, model: String) {
        self.init(maker: maker,
                  model: model,
                  year: 2023,
                  fuelLevel: 1.0)
    }
}

// Nested type
extension Car {
    enum Era {
        case vintage, classic, modern
    }
    
    var era: Era {
        switch year {
        case ...1990:
            return .vintage
        case 1991...2000:
            return .classic
        case 2001...:
            return .modern
        default:
            return .modern
        }
    }
}

// add method
extension Car {
    mutating func fillFuel() {
        fuelLevel = 1.0
    }
}


var firstCar = Car(maker: "Honda",
                   model: "Civic",
                   year: 2000,
                   fuelLevel: 0.5)
print(firstCar.fuelLevel)
firstCar.fillFuel()
print(firstCar.fuelLevel)

let secondCar = Car(maker: "Nissan", model: "Sentra")

print(firstCar.era)