Swift4 Error Cannot convert value of type '(_) -> Void' to expected argument type '(_) -> _'

Question

Using PromiseKit for API call in Swift 4:

 let apiCall = ApiManager.shared.fetchActors()
    apiCall.then { actors -> Void in
        self.dataSourceArray = actors
        self.tableView.reloadData()
        }.catch { error -> Void in

        }

I get this error:

Cannot convert value of type '() -> Void' to expected argument type '() -> _'

How do I solve this issue?

Please, see answer https://stackoverflow.com/questions/49147115/returning-void-in-promisekit-6 — Ihar Katkavets, Mar 12 '18 at 17:38

score 7 · Answer 1 · answered Dec 06 '18 at 05:10

7

Use .done Instead of using .then it will work.

answered Dec 06 '18 at 05:10

Sandeep Vishwakarma

447
6
11

score 4 · Accepted Answer · answered Mar 26 '18 at 14:54

A solution:

func fetchActorsFromApi () -> Promise<[Actor]> {
    return Promise<[Actor]> { seal in
        return Alamofire.request(API_URL).validate().responseString(completionHandler: {
            response in

            switch (response.result) {
            case .success(let responseString1):
                print (responseString1) // should be converted into the modelclass
                let actorResponse = ActorApiResponse(JSONString: "\(responseString1)")!
                seal.fulfill(actorResponse.actors!)
            case .failure(let error):
                print (error)
                seal.reject(error)
            }
        })
    }
}

What will be the syntax if i need to handle generic "Model class"/ and not just "Actor" model class. — j.krissa, Apr 23 '18 at 12:27

score 4 · Answer 3 · answered Apr 09 '18 at 13:12

let apiCall = ApiManager.shared.fetchActorFromAPI()
        let _ = apiCall.done {
            actors -> Void in
            self.dataSource = actors
            self.myTableView.reloadData()
            }.catch {
                error -> Void in
        }

use this.In the new version of PromiseKit .done() function is able to do that. Documentation : https://github.com/mxcl/PromiseKit

score 1 · Answer 4 · answered Feb 22 '18 at 16:49

1

replace .catch { error -> Void in with .catch { error in

answered Feb 22 '18 at 16:49

Hunaid Hassan

732
5
13

What about `actors`? – rmaddy Feb 22 '18 at 16:52
Same thing i guess. Remove `-> Void` – Hunaid Hassan Feb 22 '18 at 16:59
At actors section, It gives me error : Unable to infer complex closure return type; add explicit type to disambiguate. – nhuluseda Feb 23 '18 at 10:32

Swift4 Error Cannot convert value of type '(_) -> Void' to expected argument type '(_) -> _'

4 Answers4