Edge cases with default values for methods in Swift

DefaultValuesIssues.swift

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

import UIKit


protocol APIClientProtocol {
  init()
  init(urlSession: NSURLSession)
  init(apiKey: String)
  init(urlSession: NSURLSession, apiKey: String)
}

struct APIClient: APIClientProtocol {
  init(urlSession: NSURLSession = NSURLSession.sharedSession(), apiKey: String = "") {
    
  }
}

let client = APIClient()
let client2 = APIClient(urlSession: NSURLSession())
let client3 = APIClient(apiKey: "")
let client4 = APIClient(urlSession: NSURLSession(), apiKey: "")


protocol AProtocol {
  func a()
}

struct A: AProtocol {
  func a(string: String = "") {
    
  }
  
  func a() {
    
  }
}

A().a()