Creating Entity Component System

I’m implementing my first Component Entity System and am having an issue. I have a requirement that some component properties be dynamic. I do not want to create a subclass that conforms to HasExampleComponent, so this was my approach. My issue is that even though the entity contains the property I can’t cast it to HasExampleComponent.

When I create the entity I set the component like this:

entity.components[ExampleComponent.self] = .init()

I'd appreciate a template for a ECS with component properties that can be updated from the app. Thanks

public struct ExampleComponent: Component {
    public var value = 0
}

public protocol HasExampleComponent: Entity {
	var value: Int
}

public class ExampleSystem: System {
    private static let query = EntityQuery(where: .has(ExampleComponent.self))

    public required init(scene: Scene) {}
  
    public func update(context: SceneUpdateContext) {
        context.scene.performQuery(Self.query).forEach { entity in

			// this won’t work because entity doesn’t conform to HasExampleComponent
            entity.value += 1
        }
    }
}

extension Entity {

    @available (iOS 15.0, *)
    public var value: Int? {
        get { components[RotatingComponent.self].value ?? 0}
        set { components[RotatingComponent.self].value = newValue }
    }
}