无法将类型[[（string，string）]'的值分配给类型[[string：string]'

Question

I've declared this dictionary:

var arrayFrasi:[String:String] = [:]

Then in the viewDidLoad I retrive the data from my db and then I sort the dictionary using this code:

let df = NSDateFormatter()
        df.dateFormat = "dd-MM-yyyy"

        let myArrayOfTuples = self.arrayFrasi.sort{ df.dateFromString($0.0)!.compare(df.dateFromString($1.0)!) == .OrderedAscending}

But I need to use the initial dictionary ( arrayFrasi) , when I do this:

self.arrayFrasi = myArrayOfTuples

I've got this error:

cannot assign value of type '[(string, string)]' to type '[string : string]'

I can't figure out why. Thank you very much!

Answer 1

That makes perfect sense. A Dictionary has no defined order, so the sort returns you an array of tuples.

Swift's Dictionary type does not have a defined ordering. To iterate over the keys or values of a dictionary in a specific order, use the sort() method on its keys or values property.

https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/CollectionTypes.html

Answer 2

You need to Map it back into the same type

var arrayFrasi: [String: String] = [ "24-01-1991" : "VALUE" , "22-01-1991" : "VALUE" ]
let df = NSDateFormatter()
df.dateFormat = "dd-MM-yyyy"

let myArrayOfTuples = arrayFrasi.sort{ df.dateFromString($0.0)!.compare(df.dateFromString($1.0)!) == .OrderedAscending}.map { [$0.0 : $0.1] }.flatMap { $0 }
    .reduce([String:String]()) { (dict, tuple) in
        var dict = dict
        dict.updateValue(tuple.1, forKey: tuple.0)
        return dict
}

arrayFrasi = myArrayOfTuples // ["22-01-1991": "VALUE", "24-01-1991": "VALUE"]

Hope It Helps