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iOS

Posted by jonathanbello2
jonathanbello2
4,224 Points

Swift: Making a network call

Following the steps in the video of http://teamtreehouse.com/library/build-a-weather-app-with-swift/pulling-data-from-the-web/making-a-network-call

This newline of code 

let weatherData = NSData.dataWithContentsOfURL(forecastURL, options: nil, error: nil)

creates an error: 

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[_NSPlaceholderData initWithContentsOfURL:options:error:]: nil URL argument'

It points to the following line in AppDelegate.swift

class AppDelegate: UIResponder, UIApplicationDelegate {
Chris Shaw
Chris Shaw
26,676 Points

Hi Jonathan,

Could you please post your forecastURL and baseURL variables you have as the error is saying you don't have an instance of NSURL assigned to forecastURL.

jonathanbello2
jonathanbello2
4,224 Points 
let baseURL = NSURL(string: "https://api.forecast.io/forecast/\(apiKey)")
let forecastURL = NSURL(string: "32.302452, -80.975017", relativeToURL: baseURL)

3 Answers

Chris Shaw
Chris Shaw
26,676 Points

So this error is actually becoming pretty common now and it's because the NSURL constructor doesn't accept spaces in the string parameter which is something that unless you know about it doesn't make itself known as an actual error. Simply change your code so the lat,lng value you have has no space after the comma like below.

let forecastURL = NSURL(string: "32.302452,-80.975017", relativeToURL: baseURL)
jonathanbello2
jonathanbello2
4,224 Points

Thanks that did the trick. Funny thing is that I am printing out the data 

println(weatherData)

and I get nil.

agrizzle
agrizzle
1,400 Points

Chris, you're a boss! How did you find the answer?

Chris Shaw
Chris Shaw
26,676 Points

Hi Alexander,

I ran into the same issue initially when the course was released and simply eliminated the coordinates string and replace it with an empty string and that did the trick, after some light reading I found that NSURL constructors don't accept spaces unless they're URL encoded.

agrizzle
agrizzle
1,400 Points
agrizzle
agrizzle
1,400 Points

So was there something in the error message that made it clear to you that you should try eliminating the coordinates string in the first place or did you just start moving things around?

Chris Shaw
Chris Shaw
26,676 Points

Normally there's a faint orange/tanned arrow pointing up that sits beneath the area of the code where the error is, look for that and you can see what's going wrong from that point of the code onwards.

agrizzle
agrizzle
1,400 Points
agrizzle
agrizzle
1,400 Points

Cool. Thanks for being so helpful!