CODEWITHSUNDEEP
swiftrx-swift
Mr.P
Mr.P

Reputation: 1430

RxSwift protocol and concrete types

I'm having trouble with a BehaviorRelay that has a protocol type and using it on concrete types. Here's my code:

protocol Item {

    var title: { get }

}

struct Can: Item {

    let title = "Can"

}

let canRelay = BehaviorRelay<Can?>(value: nil)

func handle(item: BehaviorRelay<Item?>) {
    // do something with item here
}

handle(item: canRelay) // can't do this?

I assumed I would be able to call handle(item:) but it's not the case because the arguments don't match. I get that they don't match, but Can is a type of Item so shouldn't this be possible?

Upvotes: 1

Views: 423

Answers (1)

Daniel T.
Daniel T.

Reputation: 33967

Can may be a subtype of Item, but BehaviorRelay<Can> is not a subtype of BehaviorRelay<Item>.

Also, you should not be passing BehaviorRelays around in code. Pass Observables instead.

Once you know these two rules, you end up with:

func handle(item: Observable<Item?>) {
    // do something with item here
}

handle(item: canRelay.map { $0 })

Upvotes: 3

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