'[ResponseData]' to expected argument type 'ResponseData' - ios

Question

I'm creating an application which are fetching data from an API. I've created the "API call" in a separate class so I can use the same call multiple times. But it does not return the value as I expect it to.
In ViewController A
let data = JsonData.init()
data.downloadJsonData(urlString: urlString) { (responseArray) in
dataArray.append(responseArray)
print(self.dataArray)
}
I'm getting the error at dataArray.append(responseArray):
Cannot convert value of type '[ResponseData]' to expected argument type 'ResponseData'
In JsonData class
class JsonData{
var dataArray:[ResponseData] = []
func downloadJsonData(urlString: String, completed: #escaping (Array<ResponseData>) -> ()){
guard let url = URL(string: urlString) else {return}
URLSession.shared.dataTask(with: url) { (data, response, err) in
guard let data = data else{
return
}
do{
self.dataArray = [try JSONDecoder().decode(ResponseData.self, from: data)]
//Complete task in background
DispatchQueue.main.async {
completed(self.dataArray)
}
}
catch let jsonErr{
print(jsonErr)
}
}.resume()
}
}
I assume the problem is at:
DispatchQueue.main.async{
completed(self.dataArray)
}
So I would like to return the array back to the correct class once it fetched the data from the API. What could I have done wrong? Any help would be much appreciated.

Answer 1

The error is clear: You are using the (wrong) API for appending a single element
Replace
dataArray.append(responseArray)
with
self.dataArray.append(contentsOf: responseArray)
Side note:
Setting and later appending the items again makes no sense. Use a local variable.
Replace
self.dataArray = [try JSONDecoder().decode(ResponseData.self, from: data)]
//Complete task in background
DispatchQueue.main.async {
completed(self.dataArray)
}
with (a different name makes it clearer)
let result = try JSONDecoder().decode(ResponseData.self, from: data)
//Complete task in background
DispatchQueue.main.async {
completed([result])
}