iOS Swift：按值对数组进行排序时，将字符串转换为浮点数的位置

Question

In iOS Swift, I am sorting an array in descending order as per the below code. The code works fine, however, 'Price' is not a double but a string (so currently the code makes some mistakes when it is multi-digit numbers).

How can I convert the string 'Price' into a double within this one-line sorting function?

OfferList.sort { $0.Price > $1.Price }

I know there are ways of doing it when writing the sort as a multi-line loop, but is there a way of doing it directly in the line above?

Answer 1

Double has an initializer that can take a StringProtocol , though of course it returns an Optional since the string may or may not actually be numbers. In order to sort your strings as doubles you'll need a fallback option in case it fails, or else you'll need to force unwrap these init s if you can guarantee they'll always be doubles. The options look like this:

//Fallback using a nil-coalescing operator
OfferList.sort { (Double($0.Price) ?? 0) > (Double($1.Price) ?? 0) }

//Force unwrapping
OfferList.sort { Double($0.Price)! > Double($1.Price)! }

As a small, unrelated aside, it is considered best practice to name variables and attributes of objects in camel case, like offerList and $0.price . Not a requirement, of course, but this is what other Swift developers would be expecting.

Answer 2

Use Sorted method of NSArray to convert and Sort from Dictionary Value. Use the below code to sort.

let sortedResults: NSArray = arry.sorted { (obj1, obj2) -> Bool in
        if ((obj1 as! NSDictionary).allKeys as NSArray).contains("id") && ((obj2 as! NSDictionary).allKeys as NSArray).contains("id"){
            return Float((obj1 as! NSDictionary)["id"] as! String)! < Float((obj2 as! NSDictionary)["id"] as! String)!
        }
        else{
            return true
        }
        } as NSArray