Xcode - Swift - NSURL : “fatal error: unexpectedly found nil while unwrapping an Optional value”

Question

I'm trying to test an OAuth2 implementation in a Xcode Playground, using a PHP API and a Swift client. Basically, my code looks like this

let url = NSURL(string: "http://localhost:9142/account/validate")!
var request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"
request.HTTPBody!.setValue("password", forKey: "grant_type")
// Other values set to the HTTPBody

NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue()) { (response, data, error) in
    // Handle response here
}

But I keep getting this error when I instantiate the url variable :

fatal error: unexpectedly found nil while unwrapping an Optional value

I tried not unwrapping it when I instantiate it but rather when I use it, it didn't change anything, the error appears on the first time I unwrap it.

It keeps getting even weirder.. The following

let url = NSURL(string: "http://localhost:9142/account/validate")!
println(url)

outputs

http://localhost:9142/account/validate fatal error: unexpectedly found nil while unwrapping an Optional value

I really don't understand where the error can come from, as I'm really new to Swift

The error can easily come from request.HTTPBody! since you forced unwrapped HTTPBody. Follow this tutorial jamesonquave.com/blog/making-a-post-request-in-swift to make a post request — Zell B.
Your error isn't coming from url definition. Check the request to see HTTPBody does exist — anasimtiaz
Wow, I commented the lines I used the HTTPBody!, and it actually came from there ! I found it was from the NSURL since Xcode put the error on this line. Thanks a lot for helping me ! — k4zuk0
Please note that you will get a similar error with url definition if there is a space in the string you are using, e.g. url = NSURL(string="http://test.com/something?argument=variable containing space") — Kushal Ashok

Elliott Minns Elliott Minns · Accepted Answer · 2015-02-27T15:25:05

What is happening is you are forced unwrapping the HTTPBody which is set to nil, causing a runtime error at this line:

request.HTTPBody!.setValue("password", forKey: "grant_type")

You need to create an NSData object for your request body and then assign it to the request.HTTPBody as per the following code:

let url = NSURL(string: "http://localhost:9142/account/validate")!
var request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"

// Create a parameter dictionary and assign to HTTPBody as NSData
let params = ["grant_type": "password"]
request.HTTPBody = NSJSONSerialization.dataWithJSONObject(params, options: NSJSONWritingOptions.allZeros, error: nil)

NSURLConnection.sendAsynchronousRequest(request, queue: NSOperationQueue.mainQueue()) { (response, data, error) in
    // Handle response here
}

I hope this helps solves your problem.

Update:

In order to serialise data without using a JSON serializer, you can create your own similar to below:

func dataWithParameterDictionary(dict: Dictionary<String, String>) -> NSData? {
    var paramString = String()

    for (key, value) in dict {
        paramString += "\(key)=\(value)";
    }

    return paramString.dataUsingEncoding(NSASCIIStringEncoding, allowLossyConversion: false)
}

and call it like such:

let dict = ["grant_type": "password"]
let data = dataWithParameterDictionary(dict)
request.HTTPBody = data

Xcode - Swift - NSURL : “fatal error: unexpectedly found nil while unwrapping an Optional value”

1 Answers

Update: