Problem of result about swift array sorted

Question

I am facing a problem with array sorting.
I am trying to sort an array, but not getting the result as expected. If I want to sort when the count are the same, they also get sorted by price.
What's wrong with my approach?

self.array = items.sorted(by: { (item1, item2) -> Bool in 
                 if item1.count > item2.count {                      
                    return true                  
                 } else {                      
                    if item1.count == item2.count {
                        if item1.price > item2.price {
                            return true
                        }
                    }
                 }              
                return false
             })

this is my sort result:

[Item(name: "AAA", count: 7, price: "30737517", index: 0), 
 Item(name: "EEE", count: 3, price: "8814388", index: 4), 
 Item(name: "CCC", count: 3, price: "12100396", index: 2), 
 Item(name: "DDD", count: 1, price: "9403300", index: 3), 
 Item(name: "FFF", count: 1, price: "5072755", index: 5), 
 Item(name: "BBB", count: 1, price: "21477775", index: 1)]

When the count numbers are same, I want to sort the array by price in descending order.

price is a String I guess? Then, tell me: if you compare: "BBB" and "BBABBB", which one will be "first"? How is the comparison between Strings done? Compare characters at 0, then compare characters at 1, then compare characters at 2, etc. How is a Int compare? If you compare 10 and 2, is that the same logic? No. Transform the price into a Int or a Double. Maybe use it into your struct too as such. — Larme
– Larme, Commented Jan 7, 2019 at 7:26

vadian · Accepted Answer · 2019-01-07 08:00:08Z

1

Lexically is 10 greater than 2 but "10" is less than "2"

There are APIs to sort strings numerically

self.array = items.sorted { ($0.count >= $0.count) && $0.price.compare($1.price, options: .numeric) == .orderedAscending }

or

self.array = items.sorted { ($0.count >= $0.count) && $0.price.localizedStandardCompare($1.price) == .orderedAscending }

edited Jan 7, 2019 at 8:00

answered Jan 7, 2019 at 7:49

vadian

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Comments

Tj3n · Accepted Answer · 2019-01-07 07:36:02Z

0

Probably you would want to make your price become Int or Double in your struct or class, String comparison only compare the first character so "8814388" > "12100396", this conversion should work:

self.array = items.sorted(by: { ($0.count >= $1.count) && (Double($0.price) ?? 0 > Double($1.price) ?? 0) })

answered Jan 7, 2019 at 7:36

Tj3n

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