Skip to content

Instantly share code, notes, and snippets.

What would you like to do?
Simplified NetworkSessionInterface for fetching data tasks only
// NetworkSessionInterface.swift
// ToyPhotoGallery
// Created by Voxels on 7/6/18.
// Copyright © 2018 Michael Edgcumbe. All rights reserved.
import Foundation
/// Class used to wrap URLSession for handling data and download session tasks
class NetworkSessionInterface : NSObject {
/// The error handler delegate used to report non-fatal errors
let errorHandler:ErrorHandlerDelegate
/// The bucket handler for fetching AWS specific URLs
lazy var bucketHandler:AWSBucketHandler = AWSBucketHandler()
init(with errorHandler:ErrorHandlerDelegate) {
self.errorHandler = errorHandler
Uses a one-off URLSession, NOT the interface's session, to perform a quick fetch of a data task for the given URL
- parameter url: the URL being fetched
- parameter queue: The queue that the fetch should be returned on
- parameter timeout: The number of seconds before timing out the request
- parameter cachePolicy: The *URLRequest.CachePolicy* for handling the request. Defaults to *.returnCacheDataEleseLoad*.
- parameter cacheHandler: An optional *CacheHandler* used to archive the response
- parameter completion: a callback used to pass through the optional fetched *Data*
- Returns: void
func fetch(url:URL, on queue:DispatchQueue?, timeout:TimeInterval, cachePolicy:URLRequest.CachePolicy = .returnCacheDataElseLoad, cacheHandler:CacheHandler?, completion:@escaping (Data?)->Void) {
// Using a default session here may crash because of a potential bug in Foundation.
// Ephemeral and Shared sessions don't crash.
// See:
var fetchQueue:DispatchQueue = .main
if let otherQueue = queue {
fetchQueue = otherQueue
if AWSBucketHandler.isAWS(url: url), let filename = bucketHandler.filename(for: url) {
bucketHandler.fetchWithAWS(filename: filename, on:fetchQueue, with:errorHandler, completion: completion)
// We are handling the cacheing ourselves
let session = URLSession(configuration: .ephemeral)
let request = URLRequest(url: url, cachePolicy: cachePolicy, timeoutInterval: timeout)
if let data = cacheHandler?.cachedData(for: request) {
let taskCompletion:((Data?, URLResponse?, Error?) -> Void) = { [weak self] (data, response, error) in
if let e = error {
fetchQueue.async {
fetchQueue.async { [weak self] in
if let handler = cacheHandler {
do {
try handler.storeResponse(request:request, response: response, data: data, completion: completion)
} catch {
} else {
let task = session.dataTask(with: request, completionHandler: taskCompletion)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment