将不同的数组合并到另一个数组中

Question

struct Product {
    let id: String
    let quantity: Int
    let price: Double
}

class ProductPrices {

    internal static var PricesArray : [String:Double] = ["product1": 5.00,"product2": 5.00,"product3": 5.00]

}

class ProductNames {

    internal static var NamesArray : [String:String] = ["product1": "name1","product2": "name2","product3": "name3"]

}

I have this array

["product1","product1","product2,"product1","product3","product2"]

My question is how can I put these items into Product

Expected Result:

Product(id: "name1", quantity: 3, price: 15.00)
Product(id: "name2", quantity: 2, price: 10.00)
Product(id: "name3", quantity: 1, price: 5.00)

Answer 1

The input

So we have a struct

struct Product {
    let id: String
    let quantity: Int
    let price: Double
}

We also have 2 dictionaries and 1 array

let prices = ["product1": 5.00, "product2": 5.00, "product3": 5.00]
let names = ["product1": "name1","product2": "name2","product3": "name3"]
let elms = ["product1", "product1", "product2", "product1", "product3", "product2"]

The output

Now we want to build an array of Product(s) using the following logic

1. Product.id is retrieved from names
2. Product.quantity is the number of occurrences of Product.id into elms
3. Product.price is the price of the product * the quantity

We can achieve that writing this

let products = names.compactMap { elm -> Product? in
    let name = elm.value
    let id = name
    let quantity = elms.filter { $0 == elm.key }.count
    guard quantity > 0, let price = prices[elm.key] else { return nil }
    return Product(id: id, quantity: quantity, price: price * Double(quantity))
}

Test

[
    Product(id: "name2", quantity: 2, price: 10.0),
    Product(id: "name1", quantity: 3, price: 15.0),
    Product(id: "name3", quantity: 1, price: 5.0)
]

The compactMap method is available in Swift 4.1. For previous versions of Swift please use flatMap .

Answer 2

Although I am confused about your data structures I show you my approach. I am sure there are more elegant solutions but it works as expected:

let productArray = ["product1", "product1", "product2", "product1", "product3", "product2"]

// create products
var products: [Product] = []
for uniqueProductName in Set(productArray) {
    let quantity = productArray.filter({$0 == uniqueProductName}).count
    guard let id = ProductNames.NamesArray[uniqueProductName],
        let price = ProductPrices.PricesArray[uniqueProductName] else { continue }
    let total = price * Double(quantity)

    let product = Product(id: id, quantity: quantity, price: total)
    products.append(product)
}

Answer 3

Another solution could be

let products = ["product1","product1","product2","product1","product3","product2"]
let (prices, names) = (ProductPrices.PricesArray, ProductNames.NamesArray)

let quantities = products.reduce(into: [:]) { result, product in
    result[product, default: 0] += 1
}

// quantities: ["product2": 2, "product1": 3, "product3": 1]

let result: [Product] =  names.keys.flatMap { key in
    guard let name = names[key],
        let price = prices[key],
        let quantity = quantities[key] else {
            return nil
    }
    return Product(id: name, quantity: quantity, price: price)
}