How to handle parse JSON errors in Swift [closed] - swift

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I'm new in Swift and though I've read responses to many questions with a similar title, since there are apparently so many ways to handle HTTP calls in Swift, I'm completely confused.
I use URLSession.shared.dataTask to make HTTP calls to an open API and handle the response as
let fiatRates = try! JSONDecoder().decode(FiatResponse.self, from: data!)
DispatchQueue.main.async {
completion(fiatRates)
}
where FiatResponse is
struct FiatResponse: Decodable {
var rates: [String: Float]
var base: String
var date: String
}
When I wrap this is do-catch, I get this warning:
Catch block is unreachable because no errors are thrown in do block
Yet the app crashes with an error in the do block in case the API returns errors or times out. In. such situation the app never runs the catch block.
How can I tweak my code to correctly parse the JSON response and run the catch block, should an error occur?

Answer 1

When you add ! to try the error will not be thrown, instead it will crash the app. To make the do-catch work you need to get rid of the !:
do {
let fiatRates = try JSONDecoder().decode(FiatResponse.self, from: data!)
} catch {
print(error)
}
You can read more about it here, in this blogpost. Also, here is the full documentation.