Simple builder pattern for Swift

BuilderPatternExample.swift

import Foundation

// Usage:
//
// let car = Car(engine: "Awesome Engine", gas: 90, builder: {
//     $0.hasCooler = true
//     $0.hasSmartKey = true
// })
final class Car {
    let engine: String
    var gas: Int
    var hasCooler: Bool?
    var hasSmartKey = false
    
    typealias CarBuilder = (Car) -> ()
    
    init(engine: String, gas: Int, builder: CarBuilder) {
        self.engine = engine
        self.gas = gas
        self.hasCooler = false
        builder(self)
    }
}