ios - 如何在 swift iOS 中通过 nsurlsession 为 REST API 创建全局函数？

Question

如何创建一个函数来通过 NSURLSESSION 调用 RESTful api，该函数可以在 swift iOS 中的每个 Controller 上使用，即应用程序中任何地方的单例对象这是我想出的代码。但是一旦我调用该方法，它就会崩溃，直到返回语句为止，jsonresponse 为空。

func apicall (mainurl : String, method :String,params :String ) -> NSDictionary{

    var jsonresponse = NSDictionary()
    let url:NSURL = NSURL(string: mainurl)!
    let session = NSURLSession.sharedSession()

    let request = NSMutableURLRequest(URL: url)
    request.HTTPMethod = method
    //        request.cachePolicy = NSURLRequestCachePolicy.ReloadIgnoringCacheData

    let paramString = params
    request.HTTPBody = paramString.dataUsingEncoding(NSUTF8StringEncoding)

    let task = session.dataTaskWithRequest(request) {
        (
        let data, let response, let error) in
        enum JSONError: String, ErrorType {
            case NoData = "ERROR: no data"
            case ConversionFailed = "ERROR: conversion from JSON failed"
        }
        do{
            guard let _:NSData = data, let _:NSURLResponse = response  where error == nil else {
                print("error")
                throw JSONError.NoData
            }
            print("data = \(data), response = \(response) , error = \(error)")


            guard let json = try NSJSONSerialization.JSONObjectWithData(data!, options: []) as? NSDictionary else {
                throw JSONError.ConversionFailed
            }
            jsonresponse = json

        }
        catch let error as JSONError {
            print(error.rawValue)
        } catch let error as NSError {
            print(error.debugDescription)
        }
    }
    task.resume()

    return jsonresponse
}

}

Answer 1

NSUrlSession Reference

1.Shared seesion返回默认的session单例对象。如果您想使用自己的 session ，请创建一个方法来返回 session 的单例。

func restAPICall(requestUrl:NSURL, httpMethod:String, params:NSDictionary)
        {
            let session = NSURLSession.sharedSession()
            var dataTask: NSURLSessionDataTask;
            do
            {
                let httpData = try NSJSONSerialization.dataWithJSONObject(params, options: .PrettyPrinted)
                let request = NSMutableURLRequest.init(URL: requestUrl)
                request.addValue("application/json", forHTTPHeaderField: "Content-Type");
                request.HTTPBody = httpData
                request.HTTPMethod = "POST"

                dataTask = session.dataTaskWithRequest(request){(data, response, error) in

                    do
                    {
                        let jsonData = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableLeaves)
                        print("\(ViewController.count)----------\n" + jsonData.description + "\n--------------\n");
                        ViewController.count = ViewController.count + 1

                    }
                    catch
                    {
                        print(error)
                    }
                }


                dataTask.resume();
            }
            catch
            {
                print(error)
            }
        }