Swift guard let error: Initializer for conditional binding must have Optional type, not '[String : String]' in swift?

Question

I am getting the following error at the line of code below. My app crashes when the value is nil/empty, hence why I am trying to guard unwrap.

Error: Initializer for conditional binding must have Optional type, not '[String : String]'

guard let savedByUsers = venue.childSnapshot(forPath: "bookmarkedByUsers").value as! [String : String] else { return }

as! -> as? Conditionally unwrapping something you already force unwrapped is redundant. — John Montgomery
@JohnMontgomery the suggestion is also included in the suggestion below. — Roggie

morenoadan22 morenoadan22 · Accepted Answer · 2018-05-21T03:27:50

change to:

guard let savedByUsers: [String: String] = venue.childSnapshot(forPath: "bookmarkedByUsers").value as? [String: String] else {
    return
}

The as! forces the unwrap and causes an exception when the value is nil. Using as? will avoid that and jump into the else clause.