Array extension method for generating a look-up table

Array+LookupTable.swift

extension Array {
    /// Returns a dictionary keyed by an arbitrary attribute of an element in the array.
    ///
    /// The returned dictionary can be used for look-ups by an arbitrary attribute
    /// in an array of models with constant time complexity instead of the typical
    /// linear complexity associated with looking up elements in an unsorted list.
    ///
    /// - Parameters:
    ///     - indexClosure: Callback used to specify which attribute should be used for look-ups (usually an ID)
    func lookupTable<Index: Hashable>(indexedBy indexClosure: (Element) -> Index) -> [Index : Element] {
        return .init(uniqueKeysWithValues: map { (indexClosure($0), $0) })
    }
}