Swift Function Error: 'Float' is not convertible to 'Void'

Question

I have the following function, which generates a quick NSURLConnection request and returns the contents of the page. The function gives me an error on my return line 'Float' is not convertible to 'Void'

func getDJI(year: Int, month: Int, day: Int) -> Float {
    let baseURL = "http://geo.crox.net/djia"

    var request = NSMutableURLRequest(URL: NSURL(string: String(format:"%@/%02d/%02d/%02d",baseURL, year, month, day))!)
    httpGet(request){
        (data, error) -> Void in
        if error != nil {
            println(error)
        } else {
            return (data as NSString).floatValue
        }
    }
}

What is going wrong?

Answer 1

There are two problems here.

First, you've got a closure which is supposed to return Void and you're trying to return a Float from it, and second, you've got a function that is supposed to return a Float , but you never return anything from it.

What might make the most sense is for your outer function to return Void , and for it to accept a closure that expects a Float and returns Void :

func getDJI(year: Int, month: Int, day: Int, completion:(Float)->Void) -> Void {
    let baseURL = "http://geo.crox.net/djia"

    var request = NSMutableURLRequest(URL: NSURL(string: String(format:"%@/%02d/%02d/%02d",baseURL, year, month, day))!)
    httpGet(request){
        (data, error) -> Void in
        if error != nil {
            println(error)
        } else {
            completion((data as NSString).floatValue)
        }
    }
}

And for the record... (data as NSString).floatValue looks pretty suspicious to me...

Answer 2

Your return is inside your httpGet() closure, which is supposed to return nothing ("Void").

This looks like you're trying to take an asynchronous httpGet() function and treat it as a synchronous function. You can't do that. I don't know what httpGet() does, but it's pretty obvious that it returns immediately and calls its closure when data is downloaded.