ankittlp

func multipleHeavyAsynchronousCallBackTask(start: Int, end: Int, completionHandler: @escaping ([Int]) -> Void) {
        //1. Gets the array of numbers (A dummy heavy operation)
        HeavyOperationApi.shared.heavyNumberArray(from: start, to: end) { numbers in
            //2. Using the numbers array to fillter for Even number (A Dummy heavy operation)
            HeavyOperationApi.shared.heavyFilterEvenNumberFrom(arrayOf: numbers) { evenNumbers in
                // 3. Doing Random mapping of even numbers array (A Dummy Heavy operation)
                HeavyOperationApi.shared.heavyRandomMapping(arrayOf: evenNumbers) { number in
                    return number + 10000000
                } completion: { transformedNumbrs in
                    completionHandler(transformedNumbrs)

ankittlp

import Foundation

func printWithThreadInfo(tag: String) {
    print("Thread \(Thread.current) - \(tag) - \(Thread.isMainThread)")
}

class SomeHeavyOperationTasks {
    
    func someHeavySynchronousTask() -> [Int] {
        var number: [Int] = []

ankittlp

class WebApiClient: RequestExecutor {
    
    private var configuration: URLSessionConfiguration
    private var session: URLSession
    
    init(sessionConfiguration: URLSessionConfiguration = URLSessionConfiguration.default) {
        configuration = URLSession.shared.configuration
    
        session = URLSession(configuration: configuration)

ankittlp

// Example of One-Shot piblisher with Stream Failure. 
// As we find the value 0 in the stream, we throw an error. This error is eventually catched and replaced with Just(-1) publisher.
// But after a failed value will activates the catch operator and the pipeline will cease to react further.
struct SimpleError: Error {}
let numbers = [5, 4, 3, 2, 1, 0, 9, 8, 7, 6]

let cancellable = numbers.publisher
    .tryMap({ val in
        guard val != 0 else {throw SimpleError()}

ankittlp

enum APIError: Error, LocalizedError {
    case invalidServerResponse
    case unknown
    
    var errorDescription: String? {
        switch self {
        case .unknown:
            return "Unknown error"
        case .invalidServerResponse:
            return "Invalid Server Response"

ankittlp

var cancellable: AnyCancellable?
let url = URL(string: "https://jsonplaceholder.typicode.com/posts")!

cancellable = URLSession.shared.dataTaskPublisher(for: url)
.map { $0.data } // 1
.decode(type: [Post].self, decoder: JSONDecoder()) // 2
.replaceError(with: []) // 3
.eraseToAnyPublisher() // 4
.sink(receiveValue: { posts in 

ankittlp

let urlSessionPublisher = URLSession.shared.dataTaskPublisher(for: url)//.map { $0.data }
let subscription = urlSessionPublisher.sink(receiveCompletion: { (error) in
    print("error \(error)")
}) { (data,response) in
    print("Data \(String(data: data, encoding: .utf8)) - Response  - \(response)" )
}

ankittlp

// An AssociatedType Protocol: Request type to be implemented by Concrete Requests
protocol Request {
    associatedtype Response: Decodable // 1. A Response Type constrained to be decodable
    associatedtype ResponseParser: ResponseParserType where ResponseParser.Response == Response // 2 Response parser contrained to be confirming to ResponseParserType
    // 3 Basic properties required by a request
    var baseUrl: String { get } 
    var path: String { get }
    var method: String { get }
    
    var header: [String: String]? { get }

ankittlp

class WebApiClient: RequestExecutor {
    
    private var configuration: URLSessionConfiguration
    private var session: URLSession
    
    init(sessionConfiguration: URLSessionConfiguration = URLSessionConfiguration.default) {
        configuration = URLSession.shared.configuration
    
        session = URLSession(configuration: configuration)

ankittlp

// An AssociatedType Protocol: Request type to be implemented by Concrete Requests
protocol Request {
    associatedtype Response: Decodable // 1. A Response Type constrained to be decodable
    associatedtype ResponseParser: ResponseParserType where ResponseParser.Response == Response // 2 Response parser contrained to be confirming to ResponseParserType
    // 3 Basic properties required by a request
    var baseUrl: String { get } 
    var path: String { get }
    var method: String { get }
    
    var header: [String: String]? { get }