Utility function that decodes a dictionary in place of array

KeyedDecodingContainer+DecodeArrayAsDictionary.swift

extension KeyedDecodingContainer {
    
    /// Decodes a dictionary in place of array
    /// - Parameters:
    ///   - type: Type of the element of array should be decodable
    ///   - key: The key against which the array is present in the container
    ///   - keyPath: key path on the element type to be the key of dictionay
    /// - Returns: return the dictionary
    func decodeArrayAsDictionary<T: Decodable, Key: Hashable>(
        _ type: Dictionary<Key,T>.Type,
        forKey key: KeyedDecodingContainer<K>.Key,
        withKeyPath keyPath: KeyPath<T, Key>
    ) throws -> Dictionary<Key,T> {
        var arrayContainer = try self.nestedUnkeyedContainer(forKey: key)
        var map = Dictionary<Key,T>()
        if let count = arrayContainer.count {
            // Considering there is less likely duplicate element, adding this to improve the performance as not reserving the count may result in multiple reallocations.
            map.reserveCapacity(count)
        }
        while !arrayContainer.isAtEnd {
            // Decode the next LitmusExperiment, this makes the nested unkeyed container move to the next element in it, thus when we exhaust all the element `UnkeyedDecodingContainer.getter:isAtEnd` would be true and we will break out of this loop
            let arrayElement = try arrayContainer.decode(T.self)
            let key = arrayElement[keyPath: keyPath]
            map[key] = arrayElement
        }
        return map
    }
}