Hi,
I would like to have various kinds of generators and eventually their collection counterparts of a concrete type, say Card. This is an example with generators to illustrate my intention.
typealias Card = Int
typealias Predicate = Int
protocol CardGenerator: GeneratorType {
typealias Element = Card
// + some common functions to the protocol
}
class ConcreteGenerator: CardGenerator {
typealias Element = Card
// some complex element fetching, some implicit filtering and transforms are here
func next() -> Element? { return nil }
}
class FilteredGenerator: CardGenerator {
typealias Element = Card
let predicate: Predicate
init(predicate: Predicate) {
self.predicate = predicate
}
// some complex element fetching, multiple filters and transforms are here
func next() -> Element? { return nil }
}
func select(predicate:Predicate?) → CardGenerator {
if predicate != nil {
return FilteredGenerator(predicate:predicate!)
}
else {
return ConcreteGenerator()
}
}
I am getting:
"error: protocol 'CardGenerator' can only be used as a generic constraint because it has Self or associated type requirements”
How can I have a non-generic collection or generator protocol with specific element type tied to the protocol?
Thanks,
Stefan
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