scheme_host_components.txt

// https://stackoverflow.com/questions/7367472/why-does-url-pathcomponents-contain-an/7368129#7368129

import Foundation
let urlString1 = "http://yahoo.com/video/3" // scheme: http  | host: yahoo.com | comps ["/", "video", "3"]
let urlString2 = "video/3" // scheme: Empty  | host: Empty | comps ["video", "3"]
let urlString3 = "/video/3" // scheme: Empty  | host: Empty | comps ["/", "video", "3"]
let urlString4 = "Facebook://Feed/3" // scheme: Facebook  | host: Feed | comps ["/", "3"]
let urlString5 = "yahoo.com" // scheme: Empty  | host: Empty | comps ["yahoo.com"]
let urlString6 = "giberish://yahoo.com/video/3" // scheme: giberish  | host: yahoo.com | comps ["/", "video", "3"]

let urlStrings = [urlString1, urlString2, urlString3, urlString4, urlString5, urlString6]

func logInfo(from urls: [String]) {
    urls.forEach { (urlString) in
        let url : URL = URL(string: urlString)!
        print("scheme: \(url.scheme ?? "Empty")  | host: \(url.host ?? "Empty") | comps \(url.pathComponents) ")
    }
}

logInfo(from: urlStrings)

The most counter intuitive thing about this is that for /video/3 the pathComponents are 3. ["/", "video", "3"]. See the this SO link.