NSURL, URL and NSData, Data

Question

I'm new to Swift. I was pulling an image from the Internet when I came across NSURL and URL and NSData and Data. I'm really confused. Which ones do I use? I used the following code, but I had to convert the types as shown below. What is the proper way of doing this and what is the difference between NSURL and URL and NSData and Data? Somebody please help.

if let theProfileImageUrl = tweet.user.profileImageURL{
    if let imageData = NSData(contentsOf: theProfileImageUrl as URL){
        profileImageView.image = UIImage(data: imageData as Data)
    }
}

Answer 1

Many class names dropped the NS prefix with the release of Swift 3. They should only be used with Objective-C code. If you are writing Swift 3 code you should use only the updated classes. In this case, URL and Data.

However, URL is bridged to NSURL and Data is bridged to NSData so you can cast between them when needed.

if let theProfileImageUrl = tweet.user.profileImageURL {
    do {
        let imageData = try Data(contentsOf: theProfileImageUrl as URL)
        profileImageView.image = UIImage(data: imageData)
    } catch {
        print("Unable to load data: \(error)")
    }
}

I don't know where tweet.user.profileImageURL is defined but it appears to be using NSURL so you need to cast it to URL in your code.

Answer 2

SWIFT 5.0 + fetch on background

private func fetchImage(_ photoURL: URL?) {

    guard let imageURL = photoURL else { return  }

    DispatchQueue.global(qos: .userInitiated).async {
        do{
            let imageData: Data = try Data(contentsOf: imageURL)

            DispatchQueue.main.async {
                let image = UIImage(data: imageData)
                self.userImageView.image = image
                self.userImageView.sizeToFit()
            }
        }catch{
                print("Unable to load data: \(error)")
        }
    }
}