Swift retry operation playground

Queue Playground.swift

import Foundation

protocol Completable {
    func addCompletionOperation(on queue: OperationQueue, complete: @escaping (Self) -> Void) -> Operation
}

extension Completable where Self: Operation {
    
    func addCompletionOperation(on queue: OperationQueue, complete: @escaping (Self) -> Void) -> Operation {
        let completionOperation = BlockOperation {
            complete(self)
        }
        completionOperation.addDependency(self)
        queue.addOperation(completionOperation)
        return completionOperation
    }
}

protocol Enqueueable {
    func enqueue(in queue: OperationQueue) -> Self
}

extension Enqueueable where Self: Operation {
    func enqueue(in queue: OperationQueue) -> Self {
        queue.addOperation(self)
        return self
    }
}

final class NetworkOperation: BlockOperation, Completable, Enqueueable {
    
    var result: (URLResponse, Data)?
    var lastError: Error?
    
    init(url: URL, attemptLimit: Int) {
        super.init()
        addExecutionBlock { [weak self] in
            for _ in 1 ... attemptLimit {
                let request = URLRequest(url: url)
                do {
                    var response: URLResponse?
                    let data = try NSURLConnection.sendSynchronousRequest(request, returning: &response)
                    self?.result = (response!, data)
                    return
                } catch { self?.lastError = error }
            }
        }
    }
}

let networkQueue = OperationQueue()
let completionQueue = OperationQueue()

NetworkOperation(url: URL(string: "https://google.com")!, attemptLimit: 5)
    .enqueue(in: networkQueue)
    .addCompletionOperation(on: completionQueue) { operation in
        if let (response, data) = operation.result {
            dump(response)
            dump(data)
        } else if let error = operation.lastError {
            dump(error)
        } else {
            dump("¯\\_(ツ)_/¯")
        }
    }


// Let the playground finish.
completionQueue.waitUntilAllOperationsAreFinished()