How to solve unexpectedly found nil while implicitly unwrapping an optional value?

99% of the time the above error is caused by a force-unwrapped optional that is nil . You can fix it by avoiding it becomes nil , which is sometimes not possible, so then you use optional binding or optional chaining. Avoid using implicitly unwrapped optionals when you can, unless you have a specific need to use it.

How do I unwrap optional in Swift?

You can force unwrap an optional by adding an exclamation mark after the optional constant or variable, like this: print(email!) Now, consider the following two scenarios: Instead of having a value, email is nil .

What is unwrapped in Swift?

Unwrapping an optional means that you are now casting that type as non-optional. This will generate a new type and assign the value that resided within that optional to the new non-optional type. This way you can perform operations on that variable as it has been guaranteed by the compiler to have a solid value.

What is swift optional?

An optional in Swift is basically a constant or variable that can hold a value OR no value. The value can or cannot be nil. It is denoted by appending a “?” after the type declaration. This is a big impact on the language Swift itself because what that means is that anything non-optional types can never be nil.

How do you declare an IBOutlet property?

If you have a property defined that you want to make accessible to your storyboards, just add the @IBOutlet attribute before your property. Similarly with @IBAction to connect storyboard actions back to code. class MyViewController: UIViewController { @IBOutlet weak var likeButton: UIButton?

What problems do optionals solve Swift?

Optionals are Swift’s solution to the problem of representing both a value and the absence of a value. An optional is allowed to hold either a value or nil . Think of an optional as a box: it either contains exactly one value, or is empty. When it doesn’t contain a value, it’s said to contain nil .

What is the difference between if let and guard let in Swift?

In if let , the defined let variables are available within the scope of that if condition but not in else condition or even below that. In guard let , the defined let variables are not available in the else condition but after that, it’s available throughout till the function ends or anything.

When to look for unexpectedly found nil while unwrapping an optional value?

In 99% of cases you’ve force-unwrapped an optional with ! and it was nil, so that’s the first place to look when you run into this error. The most common scenario for the fatal error: Unexpectedly found nil while unwrapping an Optional value error is when you’ve force-unwrapped an optional and it was nil. So far so good.

When is an optional value is nil in Swift?

In Swift, an optional can either have an ordinary value, or be nil. When a variable has no value it is nil. Almost every programming language has something similar to nil. It’s undefined in JavaScript, null in Java and NULL in PHP.

Why are iboutlets implicitly unwrapped optionals in Swift?

IBOutlets, in particular, are usually implicitly unwrapped optionals. This is because your xib or storyboard will link up the outlets at runtime, after initialization. You should therefore ensure that you’re not accessing outlets before they’re loaded in.

When do optional values have to be unwrapped?

An optional value must be unwrapped before it can be used. Optional is a generic type, which means that Optional and Optional are distinct types — the type inside <> is called the Wrapped type. Under the hood, an Optional is an enum with two cases: .some (Wrapped) and .none, where .none is equivalent to nil.