How to put image to NSCache in Swift? - swift

Question

I make some code using swift 4 to load image from URL, but every time I add images to server, it took a lot of time to load it in colection view or table view. I want to try store it in NScache but i dont understand to do it. can anyone help me, I'm new in swift :(
#objc func loadPosts() {
let url = URL(string: "http://someURL/Url.php")!
var request = URLRequest(url: url)
request.httpMethod = "POST"
let body = "phomepost=\(homepost)"
request.httpBody = body.data(using: String.Encoding.utf8)
URLSession.shared.dataTask(with: request) { data, response, error in
DispatchQueue.main.async(execute: {
if error == nil {
do{
let json = try JSONSerialization.jsonObject(with: data!, options: .mutableContainers) as? NSDictionary
self.comments.removeAll(keepingCapacity: false)
self.images.removeAll(keepingCapacity: false)
self.collectionView?.reloadData()
guard let parseJSON = json else {
print("Error While Parsing")
return
}
guard let posts = parseJSON["posts"] as? [AnyObject] else {
print("Error while parseJSONing")
return
}
self.comments = posts.reversed()
for i in 0 ..< self.comments.count {
let path = self.comments[i]["path"] as? String
if !path!.isEmpty {
let url = NSURL(string: path!)!
let imageData = try? Data(contentsOf: url as URL)
let image = UIImage(data: imageData! as Data)!
self.images.append(image)
} else {
let image = UIImage()
self.images.append(image)
}
}
self.collectionView?.reloadData()
//print(posts.count)
} catch {
print(error)
}
}else{
print(error)
}
})
}.resume()
}

Answer 1

You can use something like this:
private let cache = NSCache<NSString, NSData>()
.....
func downloadImage(url: String, handler: #escaping(Data?, Error?) -> Void){
let cacheID = NSString(string: url)
if let cachedData = cache.object(forKey: cacheID) {
handler((cachedData as Data), nil)
}else{
if let url = URL(string: url) {
let session = URLSession(configuration: urlSessionConfig)
var request = URLRequest(url: url)
request.cachePolicy = .returnCacheDataElseLoad
request.httpMethod = "get"
session.dataTask(with: request) { (data, response, error) in
if let _data = data {
self.cache.setObject(_data as NSData, forKey: cacheID)
handler(_data, nil)
}else{
handler(nil, error)
}
}.resume()
} else {
// NetworkError is a custom error
handler(nil, NetworkError.invalidURL)
}
}
}
}

Answer 2

This will add a small animation while loading using image set.
let imageCache = NSCache<AnyObject, AnyObject>()
extension UIImageView {
func loadImageFromUrl(urlString: String) {
let loader1 = UIImage(named: "loaderImage1.png")
let loader2 = UIImage(named: "loaderImage2.png")
let loader3 = UIImage(named: "loaderImage3.png")
let imageArray = [loader1, loader2, loader3]
let animatedImage = UIImage.animatedImage(with: imageArray as! [UIImage], duration: 1.7)
if let imageFromCache = imageCache.object(forKey: urlString as AnyObject) as? UIImage{
self.image = imageFromCache
return
} else {
self.image = animatedImage
Alamofire.request(urlString, method: .get).response { (responseData) in
if let data = responseData.data {
DispatchQueue.main.async {
if let imageToCache = UIImage(data: data){
imageCache.setObject(imageToCache, forKey: urlString as AnyObject)
self.image = imageToCache
}
}
}
} //alamofire
}
}
}