error in FOR IN loop - arrays

Question

I am trying to run the below function for the array quandlURLs in a for in loop. I am getting an error in line "loadDataFromURL", saying :can not convert value of type [String] to expected argument of type 'Sting'. Can somebody please tell me what I am missing here. Thanks!!
class func getDataFromQuandlWithSuccess(success: ((Quandl: NSData!) -> Void)) {
let quandlGold = "https://www.quandl.com/api/v3/datasets/LBMA/GOLD.json?auth_token=xyzDP7Cj-2F_Jss7sYHf&rows=1"
quandlURLs = [quandlGold, quandlSilver,quandlPlatinum,quandlPalladium]
var index: Int
var urlData = [String]()
for index in quandlURLs {
loadDataFromURL(NSURL(string: quandlURLs[index])!, completion:{(data, error) -> Void in
//2
if let urlData[index] = data {
//3
success(Quandl: urlData[index])
//below worked and showed raw data
//print("Successful \(urlData)")
}
})
}
}
here is the loadDataFromURL function
class func loadDataFromURL(url: NSURL, completion:(data: NSData?, error: NSError?) -> Void) {
let session = NSURLSession.sharedSession()
// Use NSURLSession to get data from an NSURL
let loadDataTask = session.dataTaskWithURL(url, completionHandler: { (data: NSData?, response: NSURLResponse?, error: NSError?) -> Void in
if let responseError = error {
completion(data: nil, error: responseError)
} else if let httpResponse = response as? NSHTTPURLResponse {
if httpResponse.statusCode != 200 {
let statusError = NSError(domain:"com.raywenderlich", code:httpResponse.statusCode, userInfo:[NSLocalizedDescriptionKey : "HTTP status code has unexpected value."])
completion(data: nil, error: statusError)
} else {
completion(data: data, error: nil)
}
}
})
loadDataTask.resume()
}
}

Answer 1

All you need to do here is change for index in quandlURLs to for index in 0..<quandlURLs.count
There was also an issue with if let urlData[index] = data, because you can't use optional binding with an array, you need to define a new value, so go if let urlDataEntry = data, in which case your urlIndex array should be of type NSData.
You also don't need the var index: Int line. Int is inferred when using the for in loop on the ..< function that creates an Int array, and the index variable is usable throughout the for loop.
For example:
class func getDataFromQuandlWithSuccess(success: ((Quandl: NSData!) -> Void)) {
let quandlGold = "https://www.quandl.com/api/v3/datasets/LBMA/GOLD.json?auth_token=xyzDP7Cj-2F_Jss7sYHf&rows=1"
quandlURLs = [quandlGold, quandlSilver,quandlPlatinum,quandlPalladium]
var urlData = [NSData]()
for index in 0..<quandlURLs.count {
loadDataFromURL(NSURL(string: quandlURLs[index])!, completion:{(data, error) -> Void in
//2
if let urlDataEntry = data {
//3
urlData[index] = urlDataEntry
success(Quandl: urlDataEntry)
//below worked and showed raw data
//print("Successful \(urlData)")
}
})
}
}