Access element of the struct in array of structs - ios

Question

Hi I have a task to implement the Fleet protocol which has two functions:
addNewCar - adds a new car object to the Fleet.
- Parameter car: car to add to the Fleet
- Returns: false if the car with same id already exists in the Fleet, true – otherwise.
deleteCar - Deletes the car with the specified id from the Fleet.
- Returns: true if the car with same id existed in the Fleet, false – otherwise.
listCarsByModel - returns 10 car models containing the specified string.
If there are several cars with the same model, brand's name is added to car's model in the format "brand - car",
otherwise returns simply "car".
listCarsByBrand - returns 10 car models whose brand contains the specified string,
result is ordered by brand.
struct Car {
let id: String; // unique identifier
let model: String;
let brand: String;
}
protocol Fleet {
func addNewCar(car: Car) -> Bool
func deleteCar(id: String) -> Bool
func listCarsByModel(searchString: String) -> Set<String>
func listCarsByBrand(searchString: String) -> [String]
}
class FleetImpl: Fleet {
var cars: [Car] = []
func addNewCar(car: Car) -> Bool {
if let i = cars.firstIndex(where: { $0.id == car.id }) {
print(i)
return false
} else {
cars.append(car)
print(car)
return true
}
}
func deleteCar(id: String) -> Bool {
return true
}
func listCarsByModel(searchString: String) -> Set<String> {
}
func listCarsByBrand(searchString: String) -> [String] {
}
}
I've used method firstIndex(where:). But the function adds new car to the array with existing id. (i.e. two or more cars with the same id)
How can I access that 'id' property of Car struct in order to manipulate that data?
Please help me out
This is the test code:
func test(fleet: Fleet) {
assert(!fleet.deleteCar(id: "1"))
assert(fleet.addNewCar(car: Car(id: "1", model: "1", brand: "Lex")))
assert(!fleet.addNewCar(car: Car(id: "1", model: "any name because we check id only", brand: "any brand")))
assert(fleet.deleteCar(id: "1"))
assert(fleet.addNewCar(car: Car(id: "3", model: "Some Car3", brand: "Some Brand2")))
assert(fleet.addNewCar(car: Car(id: "4", model: "Some Car1", brand: "Some Brand3")))
var byModels: Set<String> = fleet.listCarsByModels(searchString: "Car")
assert(byModels.count == 10)
byModels = fleet.listCarsByModels(searchString: "Some Car")
assert(byModels.count == 4)
assert(byModels.contains("Some Brand3 - Some Car1"))
assert(byModels.contains("Some Car2"))
assert(byModels.contains("Some Car3"))
assert(!byModels.contains("Some Car1"))
assert(byModels.contains("Some Brand1 - Some Car1"))
var byBrand: [String] = fleet.listCarsByBrand(searchString: "Brand")
assert(byBrand.count == 10)
byBrand = fleet.listCarsByBrand(searchString: "Some Brand")
assert(byBrand.count == 4)
assert(byBrand[0] == "Some Car1")
assert(byBrand[1] == "Some Car2" || byBrand[1] == "Some Car3")
assert(byBrand[2] == "Some Car2" || byBrand[2] == "Some Car3")
assert(byBrand[3] == "Some Car1")
}
test(fleet: FleetImpl())

Answer 1

Maybe a set instead of an array would work better in this case as we're dealing with unique elements. Also note that rather than using firstIndex(where) I'm using first(where) which will return the car rather than index.
import UIKit
struct Car: Hashable {
let id: String
let model: String
let brand: String
func hash(into hasher: inout Hasher) {
hasher.combine(id)
}
}
protocol Fleet {
func addNewCar(car: Car) -> Bool
func deleteCar(id: String) -> Bool
func listCarsByModel(searchString: String) -> [String]
func listCarsByBrand(searchString: String) -> [String]
}
class FleetImpl: Fleet {
var cars = Set<Car>()
func addNewCar(car: Car) -> Bool {
guard !cars.contains(where: { $0.id == car.id }) else { return false }
cars.insert(car)
return true
}
func deleteCar(id: String) -> Bool {
guard let car = cars.first(where: { $0.id == id }) else { return false }
cars.remove(car)
return true
}
func listCarsByModel(searchString: String) -> [String] {
let searchedCars = cars.filter { $0.model.lowercased().contains(searchString.lowercased()) }.sorted { $0.brand < $1.brand }
var formattedModels = [String]()
searchedCars.forEach { car in
if let car = searchedCars.first(where: { $0.model == car.model && $0.id != car.id }) {
let carName = [car.model, car.brand].joined(separator: " - ")
formattedModels.append(carName)
} else {
formattedModels.append(car.model)
}
}
return Array(formattedModels.prefix(10))
}
func listCarsByBrand(searchString: String) -> [String] {
let searchedBrands = cars.filter { $0.brand.lowercased().contains(searchString.lowercased()) }.sorted { $0.brand < $1.brand }.map { $0.model }
return Array(searchedBrands.prefix(10))
}
}