Tusker/Tusker/AvatarCache.swift

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Swift
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2018-08-21 23:23:27 +00:00
//
// ImageCache.swift
// Tusker
//
// Created by Shadowfactson 8/21/18.
// Copyright © 2018 Shadowfacts. All rights reserved.
//
import UIKit
class AvatarCache {
static let shared = AvatarCache()
let cache = NSCache<NSString, UIImage>()
var requests = [URL: URLSessionDataTask]()
var requestCallbacks = [URL: [(UIImage?) -> Void]]()
private init() {
}
func get(_ url: URL, completion: @escaping (UIImage?) -> Void) {
let key = url.absoluteString as NSString
if let image = cache.object(forKey: key) {
completion(image)
} else if var callbacks = requestCallbacks[url] {
callbacks.append(completion)
requestCallbacks[url] = callbacks
} else {
requestCallbacks[url] = [completion]
let task = URLSession.shared.dataTask(with: url) { data, response, error in
guard error == nil,
let data = data,
let image = UIImage(data: data) else {
let callbacks = self.requestCallbacks.removeValue(forKey: url)!
for callback in callbacks {
// todo: default avatar for failed requests
callback(nil)
}
return
}
let callbacks = self.requestCallbacks.removeValue(forKey: url)!
for callback in callbacks {
callback(image)
}
self.cache.setObject(image, forKey: key)
}
task.resume()
requests[url] = task
}
}
func cancel(_ url: URL) {
requests[url]?.cancel()
requests.removeValue(forKey: url)
requestCallbacks.removeValue(forKey: url)
}
}