iOS Swift 3 create URLSession extension for synchronous and asynchronous request

Question

I'm about to create an extension for URLSession in Swift 3 to create synchronous and asynchronous request. Here is my implementation

extension URLSession {
    func sendSynchronousRequest(request: URL, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) {
        let semaphore = DispatchSemaphore(value: 0)

        let task = self.dataTask(with: request) { (data, response, error) in
            completionHandler(data,response,error)
            semaphore.signal()
        }
        task.resume()
        semaphore.wait(timeout: .distantFuture)
    }

    func sendAsynchronousRequest(request: URLRequest, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionDataTask {
        let task = self.dataTask(with: request) { data, response, error in
            completionHandler(data, response, error)
        }
        task.resume()
        return task
    }
}

I have Xcode suggest me to insert the @escaping to the function. I don't know whether the implementation is correct

I also have warning at this line:

Anyone know how to correct the extension?

score 12 · Accepted Answer · answered Nov 17 '16 at 16:46

12

I found this implementation but in swift1/2 can't remember. This is not my own. But i rewrote it in swift3. I just can't remember where i found it :/

func synchronousDataTaskWithURL(url: URL) -> (Data?, URLResponse?, Error?) {
    var data: Data?, response: URLResponse?, error: Error?

    let semaphore = DispatchSemaphore(value: 0)

    dataTask(with: url) {
        data = $0; response = $1; error = $2
        semaphore.signal()
        }.resume()

    semaphore.wait()

    return (data, response, error)
}

answered Nov 17 '16 at 16:46

Daniel Poulsen

1,446
13
21

Thanks alot. How can we use the function? for example to print out the data and then execute another serial task? is the asynchronous function correct with @escaping? – Lê Khánh Vinh Nov 17 '16 at 16:56
URLSession already has a Async function URLSession.shared.dataTask(with: , completionHandler: <(Data?, URLResponse?, Error?) -> Void>) – Daniel Poulsen Nov 17 '16 at 17:00
thanks so we can use the default async no need to wrap? I tried to use the synchronous with let data = result.0 let stringData = String(data: data!, encoding: .utf8). but have error nil. Is that the correct way? – Lê Khánh Vinh Nov 17 '16 at 17:04
http://stackoverflow.com/questions/24023253/how-to-initialise-a-string-from-nsdata-in-swift – Daniel Poulsen Nov 17 '16 at 17:13
there is not need to wrap it – Daniel Poulsen Nov 17 '16 at 17:13
Thanks! Do you think it's the properway to make a synchronous network call? (only process when call finish)? – Lê Khánh Vinh Nov 17 '16 at 17:51
In general I think it is a bad idea to use synchronized http requests. But if you really need too this is the way to do it – Daniel Poulsen Nov 17 '16 at 18:18

iOS Swift 3 create URLSession extension for synchronous and asynchronous request

1 Answers1