Identify and count array duplicates

Question

I have the following array:

var newOrderItems = [Order]()

that holds Order type elements:

let order = Order(item: itemName, quantity: 1)
newOrderItems.append(order!)

At some point newOrderItems holds:

[
Order("item1", 1),
Order("item1", 1),
Order("item2", 1),
Order("item2", 1),
Order("item3", 1),
Order("item1", 1)
]

I need to identify and count duplicate Order array elements so that I form a string message such as:

"You have ordered 3 x item1, 2 x item2, 1 x item3".

Is there a simple way for this? My solution(s) either add way too much overhead (i.e nested loops), or too much complexity (i.e. unique NSCountedSet) for something that I expect to be trivial.

• Leo Dabus: You should use a dictionary not an array

Answer 1

I would do it with a swift dictionary to manage orders like :

var newOrderItems = [Order: Int]()
if let order = Order(item: itemName, quantity: 1) {
 if newOrderItems[order] == nil {
 newOrderItems[order] = 1
 } else {
 newOrderItems[order]+=1
 }
}

And you can print details like :

var str = "You have ordered "
for order in newOrderItems.keys {
 str += "\(newOrderItems[order]) x \(order.item),"
}
print(str)

Hopefully it will help!

• Leo Dabus: That would require Order to conform to protocol Hashable

Answer 2

When you're originally appending the objects to the array, why not increase the counter there, rather than going through after, in order to save time?

• ppp: I'd need multiple counters since different types of order items can increase / decrease infinitely (theoretically).

Answer 3

how about:

var str = "You have ordered "
for object in newOrderItems {
 let itemInstancesFound = newOrderItems!.filter({ 0ドル["item"] as! String == object["item"] as! String }).count
 str += "\(itemInstancesFound) x \(object["item"] as! String),"
}

this assumes quantity is always 1 (as showed in my initial Q).