Assign a variable outside a string function in Swift 3

Question

I am struggling for a while to assign the value returned by this function to a variable outside of it, in viewDidLoad but is returning an empty string. getUid() - is returning the firebase uid prRef - is calling the firebase table for users

Can someone tell me what am I doing wrong?

Thanks in advance,

var currentWorkplaceId: String?

func getCurrentWorkplaceId() -> String {

    //completion:@escaping (Bool)->Void
    var workplaceid = String()
    prRef.child(getUid())
        .child("workplace_id")
        .observeSingleEvent(of: .value, with: { snapshot in
            workplaceid = snapshot.value as! String
    })
    return workplaceid
}

usage:

currentWorkplaceId = getCurrentWorkplaceId()

Its a mixture of synchronous (getCurrentWorkpaceId() is synchronous) and asynchronous, (observesingleevent is asynchronous). You can't mix them up like that. It is not working because the return statement is being executed before the closure is assigning the value to workplaceid. Change getCurrentWorkplaceId() to pass the value of workplaceid to the caller via a closure, in the same way observeSingleEvent is passing its value to getCurrentWorkplaceId — Piepants
– Piepants, Commented Dec 7, 2016 at 16:58

Frankie · Accepted Answer · 2016-12-07 17:02:09Z

1

observeSingleEvent is probably asynchronous with a callback. So at the time you call return, workplaceid hasn't been assigned yet. You need to do the same with your own callback.

func getCurrentWorkplaceId(_ completion: @escaping (_ workplaceId: String)->()) {

    //completion:@escaping (Bool)->Void
    prRef.child(getUid())
    .child("workplace_id")
    .observeSingleEvent(of: .value, with: { snapshot in
        completion(snapshot.value as! String)
    })
}

Usage:

getCurrentWorkplaceId() { workplaceId in
    self.currentWorkplaceId = workplaceId
}

answered Dec 7, 2016 at 17:02

Frankie

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1 Comment

Rob Over a year ago

Understood. Thanks a lot Frankie! It worked like a charm.

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