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@IBAction func othersLocation (_ sender: Any)
{
ref.child ("test"). observeSingleEvent (of: .value, with: {(snapshot) in
let value = snapshot.value as? NSDictionary
let a = value? ["userTest"] as? Double
let b = value? ["userTest2"] as? Double
print ("Location information has been acquired")
})
// Use of unresolved identifier 'a'
if let c = a
{
Use of unresolved identifier 'b'
if let d = b {
// omitted
}
}
}
When I want to declare and use data newly obtained from the database as c, b in this way
Use of unresolved identifier 'c'
Use of unresolved identifier 'd'
How do I declare it?
-
Answer # 1
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Check the variable scope.
Variables declared inside a function are local variables and cannot go out of the function.
The simplest is to create a variable to hold the value in the ViewController that holds
othersLocation.Specify an optional (?) and leave it nil until the end of reading, so that you can distinguish between before and after data acquisition.
You cannot create a constant that will be valid once the data is acquired. I think it's a good idea to use the optional.
I think the better way is to prepare a singleton "Model" and have it hold the value.