Swift Optional keyword in condition statement

These days, I am reading tech articles on way home.
Today I read Swift interview questions and found out an weird code.

if case let v? = b {
  print(v)
}

I used this optional like this.

var b: Int? = 0
        
if let v = b {
    let c = v is Int // true
}

But I didn’t know if case or let v?
Therefore I test it on Swift playground

The unwrapped value without case is not optional.

However the value with case is optional

This is weird, I have never seen case out of switch statement.
I couldn’t find anything about if let case.

But I tracking with some tests.

When I assigned nil into Variable b, if case let v block was running.

However if case let v? block was not working.

Yes, case let v? is mean an unwrapped typeof b.

But I am curious why ? not ! 🤔

We use ! to unwrap optional type variable.

Why not?

if case let v! = b

I don’t know yet when I have to use if case let yet. 😭
I guess if let v is equal to if case let v?

References

Swift Interview Questions