Trying to mock NSURLConnection

URLSessionDataTaskProtocol.swift

protocol URLSessionDataTaskProtocol {
    func resume()
}

extension NSURLSessionDataTask: URLSessionDataTaskProtocol { }

URLSessionProtocol.swift

typealias DataTaskResult = (NSData?, NSURLResponse?, NSError?) -> Void

protocol URLSessionProtocol {
    func dataTaskWithURL(url: NSURL, completionHandler: DataTaskResult) -> URLSessionDataTaskProtocol
}

extension NSURLSession: URLSessionProtocol { } // ERROR: Type 'NSURLSession' does not conform to protocol 'URLSessionProtocol'

I don't have complete context around this, but I think this gets you most of the way there:

//: Playground - noun: a place where people can play

import Foundation

protocol URLSessionDataTaskProtocol {
    func resume()
}

extension NSURLSessionDataTask: URLSessionDataTaskProtocol { }

typealias DataTaskResult = (NSData?, NSURLResponse?, NSError?) -> Void

protocol URLSessionProtocol {
    typealias Task
    func dataTaskWithURL(url: NSURL, completionHandler: DataTaskResult) -> Task
}

extension NSURLSession: URLSessionProtocol { }

Cool idea with the typealias, @eliperkins. I think the drawback to that approach is that it prevents URLSessionProtocol from being used as a concrete type, so a client wanting to use the service would have to become generic.

I'd suggest this variation for @joemasilotti:

protocol URLSessionDataTaskProtocol {
    func resume()
}

extension NSURLSessionTask: URLSessionDataTaskProtocol {}

protocol URLSessionProtocol {
    func dataTaskWithURL(url: NSURL, completionHandler: DataTaskResult) -> URLSessionDataTaskProtocol
}

typealias DataTaskResult = (NSData?, NSURLResponse?, NSError?) -> Void

extension NSURLSession: URLSessionProtocol {
    func dataTaskWithURL(url: NSURL, completionHandler: DataTaskResult) -> URLSessionDataTaskProtocol {
        return (dataTaskWithURL(url, completionHandler: completionHandler) as NSURLSessionDataTask) as URLSessionDataTaskProtocol
    }
}


func useSession(session: URLSessionProtocol) {
    session.dataTaskWithURL(NSURL(string: "http://apple.com")!, completionHandler: { (data, response, error) in
        print("Data: \(data), response: \(response), error: \(error)")
    }).resume()
}

useSession(NSURLSession(configuration: .defaultSessionConfiguration()))

This does work, thanks @briancroom!

@briancroom @joemasilotti Do you guys have Swift 3 version of this? I'm getting a Type 'URLSession' does not conform to protocol 'URLSessionProtocol' on the extension URLSession: URLSessionProtocol line.

Also getting Expressions are not allowed at the top level on useSession( line.