NSData dataWithContentsOfURL Deprecated for Swift?

I tried searching through the documentation as well as a couple of previously asked questions here on Treehouse but i can't seem to find a solution to this issue. NSData.dataWithContentsOfURL is not working in the current version of Xcode on Yosemite. The code:

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

Throws the error " 'NSString is not a subtype of 'NSURL' ".

A previous discussion surrounding this video suggested using this method instead, yet this also is no longer working:

NSData(contentsOfURL: forecastURL!)

Using the bang (!) operator gives an error of "Operand of postfix '!' should have optional type; type is 'String' " and not using the bang operator gives the error "Extra argument 'contentsOfURL' in call".

I also tried using the additional suggested arguments for contentsOfURL ("options: nil, error: nil") which also is not working.

I'm not sure how to proceed and would love some assistance.