A Struct is codable, it means all of it's properties are codable?

Question

As i understand, if a struct is codable, all properties of the struct are codable. I tried to encode an object of type PKDrawing (it's a struct in PencilKit), the type is codable, so there are no problem:

PKDrawing : Codable

And then i tried to encode a property of this object in type PKStroke

let drawing1JSON = try? JSONEncoder().encode(stroke)

but there are an error "PKStroke need to conform to Encodable"

Do i have misunderstood? and there a a way that i can encode PKStroke without implement codable manualy?