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.

You should use a dictionary not an array

Leo Dabus
– Leo Dabus

2016-04-28 20:05:28 +00:00
Commented Apr 28, 2016 at 20:05 — Leo Dabus
– Leo Dabus, Commented Apr 28, 2016 at 20:05

Muhammad Ali · Accepted Answer · 2016-04-28 20:03:30Z

2

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!

answered Apr 28, 2016 at 20:03

Muhammad Ali

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1 Comment

Leo Dabus Over a year ago

That would require Order to conform to protocol Hashable

Jay · Accepted Answer · 2016-04-29 00:59:41Z

0

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?

answered Apr 29, 2016 at 0:59

Jay

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1 Comment

ppp Over a year ago

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

ppp · Accepted Answer · 2016-05-03 05:40:49Z

0

how about:

var str = "You have ordered "

for object in newOrderItems {
    let itemInstancesFound = newOrderItems!.filter({ $0["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).

edited May 3, 2016 at 5:40

answered May 2, 2016 at 23:16

ppp

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