Dictionary Permutations of Collection Value elements

DictionaryPermutations.swift

// Folow up on Vacawama post on StackOverflow post https://stackoverflow.com/questions/64094640/every-value-combination-of-dictionary/64094971?noredirect=1#comment113341385_64094971

    extension Dictionary where Value: Collection {
        func permutations() -> [[Key: Value.Element]] {
            guard !isEmpty else { return [] }
            var permutations: [[Key: Value.Element]] = []
            permutate(&permutations)
            return permutations
        }
        private func permutate(_ permutations: inout [[Key: Value.Element]], _ dictionaries: [[Key: Value.Element]] = []) {
            if let (key, value) = first {
                var dictionary = self
                dictionary[key] = nil
                for element in value {
                    var dictionaries = dictionaries
                    if dictionaries.isEmpty {
                        dictionaries = [[key: element]]
                    } else {
                        for index in dictionaries.indices {
                            dictionaries[index][key] = element
                        }
                    }
                    dictionary.permutate(&permutations, dictionaries)
                }
            } else {
                permutations += dictionaries
            }
        }
    }

    // ***

    let dic = ["A": [1, 2, 3], "B": [4, 5, 6], "C": [7, 8, 9]]
    let result = dic.permutations()
    print(result)