Check if url image exist

Question

I'm trying to check if a url image exist using a if statement. However when trying to test it by wrong image url it keep returning:

fatal error: unexpectedly found nil while unwrapping an Optional value.

code:

var httpUrl = subJson["image_url"].stringValue
let url = NSURL(string: httpUrl)
let data = NSData(contentsOfURL: url!)

if UIImage(data: data!) != nil {
}

Answer 1

You can do it this way:

var httpUrl = subJson["image_url"].stringValue
if let data = NSData(contentsOfURL: url) {

   //assign your image here 
}

Answer 2

Other answers are telling you to unwrap the optional, but really the issue is that you are force-unwrapping the optional with !, despite it being nil.

When you write something! what you are saying is “something might be nil, but if it is, I want my program to crash”.

The reason a call might return nil is if the result is not valid – for example, if you try to fetch a key from a dictionary that isn’t there, or that a URL doesn’t point to a valid downloadable image.

You can combine the check for nil with an if statement that unwraps the optional and returns a non-optional value so long as the value wasn’t nil. You can also chain them together, so if you need to unwrap a value, then pass it into a call that also returns an optional, you can do it all in one if statement:

if let httpUrl = subJson["image_url"].string,   
       url = NSURL(string: httpUrl),
       data = NSData(contentsOfURL: url),
       image = UIImage(data: data)
{
    // use image value
}
else {
    // log some error
}

Note, on the first line, the call is to .string rather than .stringValue – .string also returns an optional with nil if the value isn’t present.

Of course, combining all these unwraps together means you can’t tell which one failed, so you may want to break them out into separate statements instead.

Answer 3

This code is tested and successful: if image url not exists no crash.

let url: NSURL = NSURL(string: "http://www.example.com/images/image.png")!
    do {
        let imgData = try NSData(contentsOfURL: url, options: NSDataReadingOptions())
        ImageView?.image = UIImage(data: imgData)
    } catch {
        print(error)
    }

Answer 4

You have to unwrap the optional like this:

if let image = data {
    // use image here
} else {
    // the data is nil
}