URLComponents+Parameters.swift

import Foundation

extension URLComponents {
    /// Abstracts away URLComponent’s array of URLQueryItems into a simple dictionary
    var parameters: [String: CustomStringConvertible] {
        get {
            return queryItems?.reduce(into: [String: String]()) { $0[$1.name] = $1.value } ?? [:]
        }
        set {
            queryItems = newValue.map { URLQueryItem(name: $0.key, value: String(describing: $0.value)) }
        }
    }
}

// Example
var comps = URLComponents(string: "http://pepe.com:81/query?a=1")!
comps.parameters["b"] = 3 // URL is now http://pepe.com:81/query?b=3&a=1
comps.parameters["a"] = nil // http://pepe.com:81/query?b=3 (a is gone)
comps.parameters = ["name": "pepe", "age": 44, "dude": true, "date": Date()] // replace all query items
comps.url // http://pepe.com:81/query?name=pepe&age=44&date=2018-01-11%2013:19:47%20+0000&dude=true

// Reading too, of course:
comps.parameters["name"] // "pepe"
comps.parameters["age"] // "44"
comps.parameters["x"] // nil