Swift result of call to is unused

Question

I cant figure out how to remove this warning in swift3:

Result of call to 'responseMessagesArray' is unused

This is how my code looks like:

fileprivate class func getMessagesAtPath(_ path: String, tokenKey: String, completionHandler: @escaping (MyMessagesWrapper?, NSError?) -> Void) {
        let credentialData = ":\(tokenKey)".data(using: String.Encoding.utf8)!
        let base64Credentials = credentialData.base64EncodedString(options: [])

        let headers = ["Accept": "application/json",
                       "Content-Type": "application/json",
                       "Authorization": "Basic \(base64Credentials)"]

        Alamofire.request(path, headers: headers)
            .responseMessagesArray { response in
                if let error = response.result.error
                {
                    completionHandler(nil, error as NSError?)
                    return
                }
                completionHandler(response.result.value, nil)
        }
    }

    class func getMyMessages(_ completionHandler: @escaping (MyMessagesWrapper?, NSError?) -> Void) {
        getMessagesAtPath(MyMessages.endpointForMyMessages(),tokenKey: MyMessages.getTokenKey(),completionHandler: completionHandler)
    }

extension Alamofire.DataRequest {
    func responseMessagesArray(_ completionHandler: @escaping (DataResponse<MyMessagesWrapper>) -> Void) -> Self {
        let responseSerializer = DataResponseSerializer<MyMessagesWrapper> { request, response, data, error in
            guard error == nil else
            {
                return .failure(error!)
            }
            guard let responseData = data else {
                return .failure(AFError.responseSerializationFailed(reason: .inputDataNil))

            }

            let JSONResponseSerializer = DataRequest.jsonResponseSerializer(options: .allowFragments)
            let result = JSONResponseSerializer.serializeResponse(request, response, responseData, error)

            switch result {
            case .success(let value):
                let json = JSON(value)
                let wrapper = MyMessagesWrapper()

                wrapper.next = json["messages"]["next_page_url"].stringValue
                wrapper.previous = json["messages"]["prev_page_url"].stringValue
                wrapper.count = json["messages"]["total"].intValue

                var allMessages:Array = Array<MyMessages>()
                print(json)
                let results = json["messages"]["data"]
                //print(results)
                for jsonAds in results
                {
                    //print(jsonAds.1)
                    let mesaggesData = MyMessages(json: jsonAds.1, id: Int(jsonAds.0))
                    allMessages.append(mesaggesData)
                }
                wrapper.myMessages = allMessages
                return .success(wrapper)
            case .failure(let error):
                return .failure(error)
            }
        }

        return response(responseSerializer: responseSerializer,
                        completionHandler: completionHandler)
    }
}

I get the warning from the fileprivate class func getMessagesAtPath() just where .responseMessagesArray { response in appears

I never had this warning in swift 2.

score 8 · Accepted Answer · answered Nov 14 '16 at 23:04

8

Assign the return value of the function to _ to explicitly discard it, like this:

_ = somethingThatReturnsAValueYouDontCareAbout()

Swift 3 warns about unused function return values, so you need to show it that you know what you're doing.

answered Nov 14 '16 at 23:04

jjs

1,338
7
19

``_ = Alamofire.request(path, headers: headers)`` worked! – user2636197 Nov 14 '16 at 23:07
2

@user2636197 Or you could simply mark the function with the `@discardableResult` attribute to let the compiler know that the return value doesn't have to be 'consumed', nor explicitly ignored (as detailed in [the linked Q&A above](http://stackoverflow.com/questions/37939573/result-of-call-to-myfunction-is-unused)) – Hamish Nov 14 '16 at 23:14

Swift result of call to is unused

1 Answers1