预期返回“ NSURLSessionDataTask”的函数中缺少返回

Question

I am following a tutorial on accessing an api and parsing the result. I am following the tutorial word for word but I cannot run the program because of 'Missing return in a function expected to return 'NSURLSessionDataTask'

so I changed the return statement to "return NSURLSessionDataTask" but then got an error saying "Cannot convert return expression of type 'NSURLSessionDataTask.Type" to return type 'NSURLSessionDataTask'

How do i figure out the return type? do I even need a return? because in the tutorial there is not return statement (i tried without return as well).

func dataTaskWithRequest(request: NSURLRequest, completionHandler: (NSData?, NSURLResponse?, NSError?) -> Void)
    -> NSURLSessionDataTask {

    let postEndpoint: String = "http://jsonplaceholder.typicode.com/posts/1"
    let urlRequest = NSURLRequest(URL: NSURL(string: postEndpoint)!)


    let config = NSURLSessionConfiguration.defaultSessionConfiguration()
    let session = NSURLSession(configuration: config)


        let task = session.dataTaskWithRequest(urlRequest, completionHandler: {
            (data, response, error) in            

        guard let responseData = data else {
            print("Error: did not recieve data")
            return
        }
        guard error == nil else {
            print("error calling GET on /posts/1")
            print(error)
            return
        }
        // parse the resutl as JSON, since that's what the API provieds
        let post: NSDictionary
        do {
            post  = try NSJSONSerialization.JSONObjectWithData(responseData, options: []) as! NSDictionary
        } catch {
            print("error trying to convert data to JSON")
            return
        }
        // now we have the post, let's just print it to prove we can access it

        print("The post is: " + post.description)

            if let postTitle = post["title"] as? String {
                print("The title is: " + postTitle)
            }




    })

    // and send it
    task.resume()



}

Answer 1

Did you really mean to write your own method called dataTaskWithRequest which looks just like the NSURLSession method of the same name? The problem is that you said you're writing a method that returns a NSURLSessionTask object, but you don't return anything.

I'd think you meant something like the following, renaming your own method to something else, and specifying that it's not returning anything itself, because it's not:

func performRequest() {
    let postEndpoint: String = "http://jsonplaceholder.typicode.com/posts/1"
    let urlRequest = NSURLRequest(URL: NSURL(string: postEndpoint)!)

    let config = NSURLSessionConfiguration.defaultSessionConfiguration()
    let session = NSURLSession(configuration: config)

    let task = session.dataTaskWithRequest(urlRequest, completionHandler: {
        (data, response, error) in

        guard let responseData = data else {
            print("Error: did not recieve data")
            return
        }
        guard error == nil else {
            print("error calling GET on /posts/1")
            print(error)
            return
        }
        // parse the resutl as JSON, since that's what the API provieds
        let post: NSDictionary
        do {
            post  = try NSJSONSerialization.JSONObjectWithData(responseData, options: []) as! NSDictionary
        } catch {
            print("error trying to convert data to JSON")
            return
        }
        // now we have the post, let's just print it to prove we can access it

        print("The post is: " + post.description)

        if let postTitle = post["title"] as? String {
            print("The title is: " + postTitle)
        }
    })

    // and send it
    task.resume()
}