How to fulfill nil promise swift

Question

I want to fulfill a promise with nil but I get error message that I cant here is my code

public static func getCurrentDevice() -> Promise<Device>{
    if let identity:[String:AnyObject] = auth?.get("identity") as! [String:AnyObject] {
        if let uuididentity = identity["uuid"]{
         return Promise { fulfill, reject in
            Alamofire.request( Router.getDevice(uuididentity as! String) )
                .responseObject { (response: Response<Device, NSError>) in
                    switch response.result{
                    case .Success(let data):
                        fulfill(data)
                    case .Failure(let error):
                        return reject(error)
                    }
            }
        }
    }
}
return Promise { fulfill, reject in
        fulfill(nil)
    }
}

I get compiler error Cannot invoke initializer for type 'Promise<>' with an argument list of type '((, _) -> _)'

score 6 · Answer 1 · answered Jul 06 '16 at 00:21

6

If the promise doesn't return a value you should use () aka Void:

return Promise { fulfill, reject in
    fulfill(())
}

If this doesn't work (I didn't test it) you could try annotate it:

return Promise<()> { fulfill, reject in
    fulfill(())
}

(Note that () is the only value of type () aka Void)

answered Jul 06 '16 at 00:21

Kametrixom

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thanks, I want to return explicit null can I do that?, I also try this and it doesn't work – Cesar Oyarzun Jul 06 '16 at 00:27
`nil` is not a valid type, if you just want to return nothing without a specific type, use `()`. If you need an optional type, use `Int?` or whatever – Kametrixom Jul 06 '16 at 00:42
I need to fulfill the promise and return nil, I did try the code you post and it doesn't work I have compiler issues. Any other idea how to do this? – Cesar Oyarzun Jul 06 '16 at 00:50
I think I found a way just adding -> Promise it works – Cesar Oyarzun Jul 06 '16 at 00:56

score 0 · Answer 2 · answered May 08 '17 at 07:40

Here you go. The question mark makes it for you in the return of the method.

public static func getCurrentDevice() -> Promise<Device?> {
        //... logic here
        let isDeviceEmpty: Bool

        if isDeviceEmpty {
            fulfill(nil)
        } else {
            fulfill(device)
        }
    }

How to fulfill nil promise swift

2 Answers2