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SOLVED: How do I capture an exception/stack trace?

Forums > 100 Days of SwiftUI
@Legion  HWS+

I have an if let and I'd like to display the error details in an alert when it fails but I'm not sure how to do that.

if let decodedUsers = try? JSONDecoder().decode([User].self, from: data) {
   users = decodedUsers
} else {
   showingError = true
   errorMessage = "Failed to decode data"
}

I'd like to replace the string literal "Failed to decode data" with an exception message or a stack trace. In C#/.NET you would use try/catch like this:

try {
   doSomething();
} catch (Exception ex) {
   errorMessage = ex.message;
}

The exception object is fed into the catch block as a parameter. How can I achieve the same thing or something similiar in swift?

   

@Hatsushira  HWS+

Write a function with your code which can fail and mark the function as throws. You should be able to catch errors in your function which you don't want to delegate to the caller and throw only those errors you want to show a message,

   

@roosterboy  HWS+

Replace this:

if let decodedUsers = try? JSONDecoder().decode([User].self, from: data) {
   users = decodedUsers
} else {
   showingError = true
   errorMessage = "Failed to decode data"
}

with something like this:

do {
    users = try JSONDecoder().decode([User].self, from: data)
} catch {
    showingError = true
    errorMessage = error.localizedDescription //you can also try "\(error)"
}

   

@Legion  HWS+

Do I have to declare error?

   

@roosterboy  HWS+

Do I have to declare error?

Nope, the compiler handles that for you.

See Handling Errors Using Do-Catch in the language guide for more details.

   

@Legion  HWS+

Thanks @roosterboy!

   

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