In Apple Swift, in what case(s) would I not want an implicitly unwrapped optional?

Question

I believe I understand why optionals are handy (my best thought for use is to be able to return a nil Boolean value), but in what case would I want to declare a wrapped optional using ? rather than ! for an implicitly unwrapped optional.

It just seems unnecessary to declare it with ? and then have to type ! all over the place rather than just using ! once.

I don't want to disregard the ? as useless, but I just can't find a use for it... Any ideas?

Answer 1

If you try to access the content of an implicitly unwrapped optional and there's nothing there, your app will crash.

If you use the patterns for checking the content of an optional — like optional binding and optional chaining - you can control how your app should fail gracefully in unforeseen situations. And it doesn't make your code all that more complicated.

Not crashing seems like a good reason to me.

Answer 2

First lets talk about what the point of ? is in swift. You might create a var that looks like this.

var number : Int?

You are basically saying that there is a possibility that this variable could be nil. If there is ever a possibility that an object could be nil, then you would not want to do something like this.

var secondNumber = number! + 5

Basically in that statement you are saying, there is a possibility this variable could be nil but, I will totally ignore that fact and pretend there is no way that it could be nil.

Instead you will want to check if that variable exists first and then set it like so

var number : Int?
var number2 : Int?

number = 10

if let unwrappedNumber = number {
    number2 = unwrappedNumber + 5
}

Hope this helps!