Extension for [String : String] to convert to http arg string

HttpArgString.swift

//
//  Extensions.swift
//  ProcessCompletion
//
//  Created by ryan teixeira on 11/2/17.
//  Copyright © 2017 Blazecore. All rights reserved.
//

import Foundation


/*
 An extension for [String : String] to convert it to a string of key=value pairs
 suitable for use as a parameter string for a url.
 
 let params = ["key1" : "value1", "key2" : "value2", "key3" : "value3"]
 let argStr = params.toHttpArgString()
 
 key1=value1&key2=value2&key3=value3
 */

protocol ArgType {}

extension String: ArgType {}

extension Dictionary where Key: ArgType,  Value: ArgType  {

    // Implement using a loop
    func toHttpArgString() -> String {
        var r = String()
        for (n, v) in self {
            if !r.isEmpty { r += "&" }
            r += "\(n)=\(v)"
        }
        return r
    }
}

//params.toHttpArgString()