Completion handler swift 3 return a variable from function

user_7599104 0
Viewed 21266

I am confused surrounding the syntax for a completion handler in swift 3.

In the function below, after parsing an xml file from a web service call, it should return a variable (an array [String:String]).
My attempt is below, but obviously it is incorrect.

  enum HistoryKey {
  case success([String:String])
  case failure(String)
 }

 private func getHistoryKeys(searchterm: String, completion: @escaping () -> HistoryKey) {
    let url = PubmedAPI.createEsearchURL(searchString: searchterm)
    let request = URLRequest.init(url: url as URL)
    let task = session.dataTask(with: request) { (data, response, error) in

        if let theData = data{
            let myParser = XMLParser.init(data: theData)
            myParser.delegate = self
            myParser.parse()
        }
    }
    task.resume()

    if keys.isEmpty {
        return .failure("no historyKeyDictionary")
    }else{
        return .success(keys)
    }

}// End of func

I want to use this function as follows

 let result = self.getHistoryKeys(searchTerm)
completionhandler swift3 swift ios
6 Answers

Swift 4.2

enum HistoryKey {
    case success([String:String])
    case failure(String)
}

func myFunction(str: String, completionHandler: @escaping (HistoryKey) -> ()){
     completion(.success([String:String]))
     //OR
     completion(.failure(""))
}

myFunction(str: String) { result in 
    switch result {
       case .success(let data): break;
       case .failure(let error): break;
    }
}

OR

func myFunction(str: String, completionHandler: @escaping (String) -> ()){
     completionHandler("")
} 

myFunction(str: "someThing", completionHandler: {(str) in

})
user_56938260
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