Swift Array of Types element not recognised as type

Question

I have the following implementation of some GKStates

import GameplayKit.GKState

class Running: GKState {
    let validNextStates: [GKState.Type] = [Paused.self, Over.self]
    
    override func isValidNextState(_ stateClass: AnyClass) -> Bool {
        return self.validNextStates.contains(where: { stateClass is $0 })
    }
}

class Paused: GKState {}

class Over: GKState {}

Does anyone have a hint on why I get Expected type after 'is' at $0? validNextStates is defined as an array of GKState Types so why is one of it's elements not recognised as a Type?

Edit:

Xcode: Version 12.1 (12A7403)

Answer 1

The problem is the type of stateClass. stateClass is of type AnyClass, which is just a typealias for AnyObject.Type and hence stateClass is a meta-type, not a normal type, so the is operator cannot be used on it.

However, to compare meta types, you can use the equality operator.

class Running: GKState {
    let validNextStates: [GKState.Type] = [Paused.self, Over.self]

    override func isValidNextState(_ stateClass: AnyClass) -> Bool {
        return self.validNextStates.contains(where: { $0 == stateClass })
    }
}

class Paused: GKState {}
class Over: GKState {}
class Invalid: GKState {}

Running().isValidNextState(Paused.self) // true
Running().isValidNextState(Invalid.self) // false