CODEWITHSUNDEEP
swiftreactive-cocoa
r.izumita
r.izumita

Reputation: 450

How to extend SignalProducerType of ReactiveCocoa4

I try extending SignalProducerType with SequenceType value. But I can't do. 'Type of expression is ambiguous without more context' error occurs in compiling. 

protocol TranslatorType {
    typealias Source
    typealias Destination
    func translate(source: Source) -> Destination
}

extension SignalProducerType where Value: SequenceType {
    func translate<T: TranslatorType, U: SequenceType where T.Source == Value.Generator.Element, T.Destination == U.Generator.Element>(translator: T) -> ReactiveCocoa.SignalProducer<U, Error> {
        return lift { $0.map { seq in seq.map(translator.translate) } } # Type of expression is ambiguous without more context error
    }
}

How can I do that?

Upvotes: 0

Views: 104

Answers (1)

Cosyn
Cosyn

Reputation: 4987

The map function of SequenceType returns an array, you can't map to a generic SequenceType. Change type U to an array, it can compile:

extension SignalProducerType where Value: SequenceType {
    func translate<T: TranslatorType, V where T.Source == Value.Generator.Element, T.Destination == V>(translator: T) -> ReactiveCocoa.SignalProducer<[V], Error> {
        return lift {  $0.map { seq in seq.map(translator.translate) } }
    }
}

Upvotes: 1

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