How to return a modified result in a promise as a promise

Question

I'm using promiseKit 6 with the extensions for Alamofire. In the function bellow I'm looking to return Promise<JSON> (I use swiftyJson) but the response from the alamofire call is a Promise containing a tuple: Promise<(json: Any, response: PMKAlamofireDataResponse)>

when I get that from the first then, how can I continue to return just the json part? thanks :)

return firstly {
  self.requestClient.request(url, method: .get, parameters: nil, encoding: JSONEncoding.default, headers: nil).responseJSON()
}.then { arg in
  let (json, rsp) = arg
  return json
}

I also get this error: Cannot convert return expression of type 'Promise<_.T>' to return type 'Promise<JSON>' on the line: }.then { arg in ...

Lory Huz · Accepted Answer · 2018-06-21T12:42:00.103

1

You should cast Any to JSON, try this (not tested), but documentation said you could use map/compactMap https://github.com/mxcl/PromiseKit/blob/master/Documentation/CommonPatterns.md

return firstly {
    self.requestClient.request(url, method: .get, parameters: nil, 
          encoding: JSONEncoding.default, headers: nil).responseJSON()
}.compactMap { data, rsp in
   return data as? JSON
}

edited Jun 21 '18 at 12:42

answered Jun 14 '18 at 11:16

Lory Huz

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I'm using The promisekit alamofire extension so the request returns a promise of type: `Promise<(json: Any, response: PMKAlamofireDataResponse)>` when you call responseJSON() on it, I've updated the question – SamAko Jun 14 '18 at 14:10
I think it's a compiler type problem, but can you try the syntax I've updated ? you could try to infer the promise type too – Lory Huz Jun 14 '18 at 14:36
Ok, I'm going to try it – SamAko Jun 14 '18 at 16:02
How it's going on ? – Lory Huz Jun 19 '18 at 14:34
worked out for me, had to remove the `in` from firstly though. – SamAko Jun 21 '18 at 07:14

How to return a modified result in a promise as a promise

1 Answers1