A map method for Dictionary that lets you easily transform its keys and values into other types

DictionaryMap.swift

extension Dictionary {
    func map<K: Hashable, V>(_ transform: (Element) throws -> (key: K, value: V)) rethrows -> [K : V] {
        var transformed = [K : V]()

        for pair in self {
            let transformedPair = try transform(pair)
            transformed[transformedPair.key] = transformedPair.value
        }

        return transformed
    }
}

let dictionary = [
    "hello": 1,
    "world": 2
]

let transformed = dictionary.map { pair in
    return (pair.key, Double(pair.value))
}