Error parsing JSON Dictionary with Swift decodable - json

Question

I receive the following error:
Error serialising json typeMismatch(Swift.Dictionary, Swift.DecodingError.Context(codingPath: [], debugDescription: "Expected to decode Dictionary but found an array instead.", underlyingError: nil))
Code:
//---------------
struct Currency: Decodable {
let symbol: String
let price: String
}
var myDict: [Currency] = []
//---------------
func testParse(){
let jsonUrlString = "https://api.binance.com/api/v3/ticker/price"
guard let url = URL(string: jsonUrlString) else
{ return }
URLSession.shared.dataTask(with: url) { (data,response,err) in
guard let data = data else
{
print("Error: No data to decode")
return
}
do
{
let exchanges = try
JSONDecoder().decode(Currency.self, from: data)
let X: [Currency] = [exchanges]
self.myDict = X
self.testFunc()
print("binance: "+self.myDict[0].symbol + ": "+self.myDict[0].price)
}
catch let jsonErr
{
print("Error serialising json",jsonErr)
}
}
.resume()
}
Is the issue with my struct layout? Or would it be how I'm parsing? I'd like to get a better understanding here for future reference. Therefore, if anyone could link a good Swift 4 guide it would be greatly appreciated. Alternatively, if you could give me a detailed answer that would be great (rather than spoon feeding the answer where I don't learn).

Answer 1

Please read the error message carefully and learn to understand it. It's very clear.
Expected to decode Dictionary but found an array instead
In other words: You want to decode a dictionary (Currency) but in truth it's an array ([Currency]).
In terms of Decodable a dictionary is the target struct or class.
And please don't name an object as ...dict which is actually an array.
var myArray = [Currency]()
...
let exchanges = try JSONDecoder().decode([Currency].self, from: data)
self.myArray = exchanges