Use Post request response string in another method Swift - ios

Question

I am trying to use response of the post request in prepareForSegue function. i want to assign response value to destination viewController property. i can not do that because when i assign it in side closure brackets, does not assign before view the new window. because inside the closure code read, after view the new window.
as well as i try to assign saveInvoice function assign to a variable and use within prepareForSegue function. but that variable is NSUrlSessionDataTask type, so i could not use it further.
bellow i have mentioned my code segment
calling function
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let previewVC :PreviewViewController = segue.destinationViewController as! PreviewViewController
previewVC.invoiceSummary = "test hash key"
let invoiceSave = saveInvoice({ hash_key in
print(hash_key)
let test = hash_key
if test != ""
{
print("Success")
}
previewVC.sendersName = "sender view controller name"
})
print(invoiceSave)
}
This is the function which handdle the post request
func saveInvoice(completionHandler: (NSString) -> Void) -> NSURLSessionDataTask
{
let invoiceSummary = "Sample invoice summary"
let invoiceDate = "2015-11-20"
let invoiceConnectionID = "647193"
//let json = ["summary": invoiceSummary, "date": invoiceDate, "business_id": invoiceConnectionID]
let json = NSMutableDictionary()
json.setValue(invoiceSummary, forKey: "summary")
json.setValue(invoiceDate, forKey: "2015-11-20")
json.setValue(invoiceConnectionID, forKey: "business_id")
let data = try? NSJSONSerialization.dataWithJSONObject(json, options: NSJSONWritingOptions(rawValue: 0));
let request = NSMutableURLRequest(URL: NSURL(string: "https://livetest.somedomain.com/api/invs?auth_token=jmkm6ijijejf23kmkdd")!)
request.HTTPMethod = "POST"
request.addValue("application/json",forHTTPHeaderField: "Content-Type")
request.addValue("application/json",forHTTPHeaderField: "Accept")
request.HTTPBody = data
var outer = ""
let task = NSURLSession.sharedSession().dataTaskWithRequest(request){
data, response, error in
let responceJSon = JSON(data: data!)
//let text = self.passJson(responceJSon)
let invoice = responceJSon["invoice"]
let hash_key = invoice["hash_key"].stringValue
let statement_number = invoice["statement_no"].stringValue
let statement_summary = invoice["summary"].stringValue
let statement_date = invoice["date"].stringValue
let obj = ["hash_key": hash_key, "statement_no": statement_number, "summary": statement_summary, "date": statement_date]
self.invObject.append(obj)
//self.invObject.append(text as! [String : String])
outer = self.invObject[0]["statement_no"]!
print(outer)
if let hash_key = invoice["hash_key"].string{
completionHandler(hash_key)
return
}
}
task.resume()
return task
}

Answer 1

First of all the saveInvoice executes asynchronously so you won't have the value when the next controller loads but a while after.
To save the variable you need to do that inside the completion block. I guess it's the hash_key that is of interest here?
so you would instead do something like this
saveInvoice({ hash_key in
previewVC.hash_key = hash_key
previewVC.sendersName = "sender view controller name"
})
However, as mentioned above this executes asynchronously so I rather think it would be better to start the save and then execute the segue programatically when the completion handler is called from within saveInvoice
saveInvoice({ hash_key in
savedHashKey = hash_key
self.performSegueWithIdentifier(segueName, sender: self)
})
and then in prepareForSegue
let savedHashKey:String? = nil
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let previewVC :PreviewViewController = segue.destinationViewController as! PreviewViewController
previewVC.invoiceSummary = savedHashKey
savedHashKey = nil
}