How to convert Array to Dictionary while keeping the same order Swift

Question

Hey I have been looking at some really good question on here. About how to convert a Array to a dictionary but the problem is that is doesn't keep the same order Example:

list = ["test", "test2", "test3"]

outPut:

listNewFromExt = ["test": "test","test3": "test3", "test2": "test2"]

Basically test3 is being switched places with test2

Code:

let listNewFromExt = list.toDictionary{($0, $0)}

extension Sequence {
 public func toDictionary<K: Hashable, V>(_ selector: (Iterator.Element) throws -> (K, V)?) rethrows -> [K: V] {
    var dict = [K: V]()
    for element in self {
        if let (key, value) = try selector(element) {
            dict[key] = value
        }
    }

    return dict
}

}

Also if you could tell me how to just make the .values "nil" instead of a copy of the key that would be great lol.

Answer 1

In Swift, a Dictionary is an unordered collection by design. Therefore you can't keep any order to it after migrating from an Array.

If you want your values to be nil, just use

let dict = Dictionary<Int, Any?>(uniqueKeysWithValues: [1, 2, 3].map { ($0, nil) })

This evaluates to [2: nil, 3: nil, 1: nil]

If you want some sort of sorting (no pun intended), you may convert the dict to a sorted tuple array:

let sortedTupleArray = dict.sorted { $0.key > $1.key }

This evaluates to [(key: 3, value: nil), (key: 2, value: nil), (key: 1, value: nil)]