Swift Enums as Result Type --

Swift-Enums-Types-Test1.playground

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

import PlaygroundSupport
import UIKit
import Foundation

PlaygroundPage.current.needsIndefiniteExecution = true
URLCache.shared = URLCache(memoryCapacity: 0, diskCapacity: 0, diskPath: nil)


//https://mislavjavor.github.io/2017-04-19/Swift-enums-are-sum-types.-That-makes-them-very-interesting/?utm_content=buffer55854&utm_medium=social&utm_source=facebook.com&utm_campaign=buffer

struct ProductExample {
    
    let a: Bool
    let b: Bool
}

let first = ProductExample(a: true, b: true)
let second = ProductExample(a: true, b: false)
let third = ProductExample(a: false, b: true)
let fourth = ProductExample(a: false, b: false)


struct ProductExampleTwo {
    let a: Bool
    let b: Int8
}

/*
 
 Sum types (in swift) are enums!
 
 Number of possible values of a sum type is the sum of the number of possible values of it’s constituent parts
 */



enum SumExample {
    case a(Bool)
    case b(Bool)
}

let firstEnum = SumExample.a(true)
let secondEnum = SumExample.b(true)
let thirdEnum = SumExample.a(false)
let fourthEnum = SumExample.b(false)


enum SumExampleTwo {
    case a(Bool)
    case b(Int8)
}




//let someUrl:URL = URL(string:"http://www.yahoo.com/")!
//I did not expect this to be valid url:
//let someUrl:URL = URL(string:"http://www.yahoooooo.com/")! //to invoke optional error
let someUrl:URL = URL(string:"http://www.yahoboo.com/")! //to error

enum Result {
    case success(URLResponse)
    case error(Error)
}

typealias Handler = (Result) -> Void

func getUser(from: URL, completionHandler: @escaping (Handler)) {
    // implementation
    
   // var request = URLRequest(url: URL(string: "http://example.com")!)
     var request = URLRequest(url: from)
    request.httpMethod = "POST"
    let session = URLSession.shared
    
    session.dataTask(with: request) {(data, response, err) in
        print("Entered the completionHandler")
        
        guard let _:Data = data as Data?, let _:URLResponse = response, err == nil else {
            print(#line, #function, "[dbg-err]: ", err!.localizedDescription)
            completionHandler(Result.error(err!))
            return
        }
        
        //completionHandler(response as! Result)
        
        print("[data]: ", data!)
        print("[response]: ", response!)
      
        
        
        
        //Testing 'response' values, mainly header access:
        
        let httpResponse = response as! HTTPURLResponse
        let statusCode = httpResponse.statusCode
        
        //Note: Different Server response(HTTPURLResponse) will give different response values
        //So accordingly - allHeaderFields will vary depending on this response(HTTPURLResponse)
        print("\n")
        let vr = httpResponse.allHeaderFields["Content-Type"]
        print(#line, #function, " dbg-vr-]:", vr!)
        let vr0 = httpResponse.allHeaderFields["Content-Encoding"]
        print(#line, #function, "dbg-vr0]:", vr0!)
        let vr1 = httpResponse.allHeaderFields["Content-Length"]
        print(#line, #function, "dbg-vr1]:", vr1!)
        let vr2 = httpResponse.allHeaderFields["Cache-Control"]
        print(#line, #function, "dbg-vr2]:", vr2!)
        let vr3 = httpResponse.allHeaderFields["X-AspNetMvc-Version"]
        print(#line, #function, "dbg-vr3]:", vr3!)
        let vr4 = httpResponse.allHeaderFields["X-AspNet-Version"]
        print(#line, #function, "dbg-vr4]:", vr4!)
        let vr5 = httpResponse.allHeaderFields["X-Powered-By"]
        print(#line, #function, "dbg-vr5]:", vr5!)
        let vr6 = httpResponse.allHeaderFields["Server"]
        print(#line, #function, "dbg-vr6]:", vr6!)
        let vr7 = httpResponse.allHeaderFields["Vary"]
        print(#line, #function, "dbg-vr7]:", vr7!)
        let vr8 = httpResponse.allHeaderFields["Date"]
        print(#line, #function, "dbg-vr8]:", vr8!)
        print("\n")
        
        if (statusCode == 200) {
                print(#line, #function, "[dbg-statusCode]: ", statusCode)
        }
        
        completionHandler(Result.success( response!))
        
        }.resume()
    
   // print(#line, #function, "[dbg-Handler]:", Handler.self)
}


//use case:
getUser(from: someUrl) { (response) in
   // print(#line, #function, "dbg-response-101 ")
    print(#line, #function, "dbg-response]: ", response)
    switch response {
    case .success(let result):
        print(#line, #function, "[dbg-000]: ", result)
        
        let httpResponse = result as! HTTPURLResponse
        let statusCode = httpResponse.statusCode
         print(#line, #function, "[dbg-2-httpResponse.]: ", httpResponse.allHeaderFields)
    
        if (statusCode == 200) {
            print(#line, #function, "[dbg-2-statusCode]: ", statusCode)
        }
        
    case .error(let error):
        print(#line, #function, "[dbg-111]: " ,error.localizedDescription)
    }

}




//Enums syntax quick & dirty

//Swift enums can be written like this:

enum Foo1 {
    case a
    case b
}

let sth1 = Foo1.a
let oth1 = Foo1.b


//But can be also written like this:
enum Foo {
    case a(String)
    case b(isEnabled: Bool)
}

let sth = Foo.a("Hello")
let oth = Foo.b(isEnabled: false)