0002-dependency-injection-using-property-wrappers-004.swift

class ProductsCalculator {
    private let taxesCalculator: TaxesCalculatorType

    // ...

    init(taxesCalculator: TaxesCalculatorType) {
        self.taxesCalculator = taxesCalculator
    }

    func calculateTotal() -> Double {
        let subtotal = products.map({ $0.price }).reduce(0, +)
        return taxesCalculator.applyTaxes(to: subtotal)
    }
}