如何在Swift中控制从NSData（contentsOfURL：url）返回的nil值？

Question

I want get data with a url in swift from php server. But when i use NSData(contentsOfURL: url!) I get nil, and my app broke with error: 'fatal error: unexpectedly found nil while unwrapping an Optional value'. This is because my server Service is Temporarily Unavailable

My code is:

  let strURL: String = "http://domain.com/myphpfile.php?username="+userTF.text!+"&pass="+passTF.text!
    let url = NSURL(string: strURL)
    let dataURL = NSData(contentsOfURL: url!)  //Here return nil

How can I control when my link returning nil I show a message but my app not close?

Thanks!

Answer 1

Avoid using forced-unwrapped values with ! , safely unwrap with if let instead:

if let url = NSURL(string: strURL), let data = NSData(contentsOfURL: url) {
    // use `data` here
} else {
    print("something went wrong")
}

Hint: don't use NSData contentsOfURL anyway, use something like NSURLSession instead. This is because contentsOfURL blocks the main thread while working which freezes the UI and could result in the app being killed by iOS.