Swift: Determine if a array of custom objects contains a particular string

Question

I have an array called carArray which is an array of Cars.
How can I write a function to determine if the array contains a specific model? For example if a user inputs "BMW", how can I determine if that is in the array? I am trying to avoid answering this problem with writing a for loop to loop through the entire array each time this happens.

struct Car {
    var make: String?
    var model: String?
    var year: Double?
}

var carArray: [Car] = []

carArray.append(Car(make: "Audi", model: "S5", year: 2015))
carArray.append(Car(make: "BMW", model: "X3", year: 2016))
carArray.append(Car(make: "Honda", model: "Accord", year: 2018))

Answer 1

Add something like this

func contains(make: String) -> Bool {
    carArray.compactMap(\.make).contains(make)
} // returns true in your case for "BMW"

This has two parts. First, I am mapping the array of Car objects to an array of String? by mapping over the make key path. Since this may have nil values, I am using compactMap to remove the nil values.

If you are going to be doing this a lot and don't want the overhead of mapping and checking every time then create something to store your cars. Something like this:

struct Car {
    var make: String?
    var model: String?
    var year: Double?
}

struct CarStore {
    private(set) var  storage: [Car] = .init()
    private var makes: Set<String> = .init()

    mutating func add(car: Car) {
        storage.append(car)
        car.make.map { makes.insert($0) } // map to run the closure only if make is not nil
    }

    func contains(make: String) -> Bool {
        makes.contains(make)
    }
}

var store = CarStore()

store.add(car: Car(make: "Audi", model: "S5", year: 2015))
store.add(car: Car(make: "BMW", model: "X3", year: 2016))
store.add(car: Car(make: "Honda", model: "Accord", year: 2018))

store.contains(make: "BMW") // -> true