Home/ Questions/fatal error: unexpectedly found nil while unwrapping an optional value. How to fix it?
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Dr. Cindy Dooley II
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Asked: 2022-07-05T15:42:53+00:00 In:

fatal error: unexpectedly found nil while unwrapping an optional value. How to fix it?

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This is an error message I see in my project: fatal error: unexpectedly found nil while unwrapping an optional value.

Here’s my example code:

let username:String? = “Alice”
let message = “Welcome, ” + username!
print(message)
// Output: Welcome, Alice

I’ve read a few docs but haven’t found the answer yet. Experts please provide a solution to help me deal with this asap. Thanks very much

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1 Answer

  1. Best Answer
    Expert

    The cause: When you encounter the fatal error: unexpectedly found nil while unwrapping an optional value, you need to pay attention to that you forced open an optional with ! while it was nil.

    Let’s assume that this code is capable of running even before the user has signed in. When a user is not logged in, the username field is null. As a result, it is optional.

    Solution:

    Solve the problem like this:

    Before forcing the unwrapping of username, you use if-statement to see whether username is null. The code enclosed in the brackets { } is not run when username is nil.

    let username:String? = nil

if username != nil {
let message = “Welcome, ” + username!
print(message)
}

     

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