Swift- Use of unresolved identifier - xcode

Question

I have the following Swift code where I am sending a POST request to a webserver and receiving a value back. The error that I receive is on the second to last line saying "Use of unresolved identifier"
func download_request() -> String {
let url:NSURL = NSURL(string: "http://url.com/read.php")!
let session = NSURLSession.sharedSession()
let request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"
request.cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringCacheData
let paramString = "data=name"
request.HTTPBody = paramString.dataUsingEncoding(NSUTF8StringEncoding)
let task = session.downloadTaskWithRequest(request) {
(let location, let response, let error) in
guard let _:NSURL = location, let _:NSURLResponse = response where error == nil else {
print("Error")
return
}
let urlContents = try! NSString(contentsOfURL: location!, encoding: NSUTF8StringEncoding)
guard let _:NSString = urlContents else {
print("Error")
return
}
}
task.resume()
return urlContents
}
How would I fix this error? I think that it means that I cannot use urlContents outside of the let task = session.downloadTaskWithRequest(request) { } but how would I declare the variable so that I can use it outside?

Answer 1

Try declaring urlContents outside of the session.downloadTaskWithRequest(request) { } block. Like so:
func download_request() -> String? {
let url:NSURL = NSURL(string: "http://url.com/read.php")!
let session = NSURLSession.sharedSession()
var urlContents: NSString?
let request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"
request.cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringCacheData
let paramString = "data=name"
request.HTTPBody = paramString.dataUsingEncoding(NSUTF8StringEncoding)
let task = session.downloadTaskWithRequest(request) {
(let location, let response, let error) in
guard let _:NSURL = location, let _:NSURLResponse = response where error == nil else {
print("Error")
return
}
urlContents = try? NSString(contentsOfURL: location!, encoding: NSUTF8StringEncoding)
guard let _:NSString = urlContents else {
print("Error")
return
}
}
task.resume()
return (urlContents as! String)
}
Then when you need to use urlContents unwrap it with an if let binding
if let contents = download_request() {
//Use safely unwrapped contents
}

Answer 2

You could make return type optional like below
func download_request() -> String? {
var urlContents: String?
....
....
let task = session.downloadTaskWithRequest(request) {
(let location, let response, let error) in
...
...
...
guard let _:NSURL = location, let _:NSURLResponse = response where error == nil else {
print("Error")
return
}
urlContents = try! NSString(contentsOfURL: location!, encoding: NSUTF8StringEncoding) as String
guard let _:NSString = urlContents else {
print("Error")
return
}
}
task.resume()
return urlContents
}
And call the method like
if let request = download_request() {
//do anything with your request
}
Suggesting you to rename your method properly since you are returning the downloaded data not the request.
And this is not the correct way to get your downloaded data back as a return to the method since the completionHandler will be called once the operation is done so urlContents will be nil. Hence create another method which takes String as input and call it within the completionHandler of downloadTaskWithRequest