I've defined a Struct like this

```
struct CartItem {
    var name: String
    var quantity: NSString
    var price: NSString
}

```

Now, i want to calculate a total of cart and write it in a label, `quantity * price`.
But, i have to use NSString because there are quotes in my numeric values.

In my tableviewcell i can show the value with "as String". But if i have to calculate a simple sum of price like this: 

```
let sum = CartItems.lazy.map { $0.price }.reduce(0, +) 

```

it returns an error: Cannot convert value of type 'NSString' to closure result type 'Int'.

Someone can help me with this?