My first choice would be to query for all the users between 20 and 25 and then filter in code for ones with a distance < 100.
The question states filtering in code is not an option but I wanted to include it for completeness for situations where it was several thousand nodes or less:
struct User { //starting with a structure to hold user data
var firebaseKey : String?
var theAge: Int?
var theDistance: Int?
}
var userArray = [User]() //the array of user structures
usersRef.queryOrderedByChild("age").queryStartingAtValue(20)
.queryEndingAtValue(25).observeEventType(.Value, withBlock: { snapshot in
for child in snapshot.children { //.Value so iterate over nodes
let age = child.value["age"] as! Int
let distance = child.value["distance"] as! Int
let fbKey = child.key!
let u = User(firebaseKey: fbKey, theAge: age, theDistance: distance)
userArray.append(u) //add the user struct to the array
}
//the array to contain the filtered users
var filteredArray: [User] = []
filteredArray = userArray.filter({$0.theDistance < 100}) //Filter it, baby!
//print out the resulting users as a test.
for aUser in filteredArray {
let k = aUser.firebaseKey
let a = aUser.theAge
let d = aUser.theDistance
print("array: \(k!) \(a!) \(d!)")
}
})
}
Now a potential super simple answer.
let usersRef = self.myRootRef.childByAppendingPath("users")
usersRef.queryOrderedByChild("age").queryStartingAtValue(20)
.queryEndingAtValue(25).observeEventType(.ChildAdded, withBlock: { snapshot in
let distance = snapshot.value["distance"] as! Int
if distance < 100 {
let age = snapshot.value["age"] as! Int
let fbKey = snapshot.key!
print("array: \(fbKey) \(age) \(distance)")
}
})
Notice that we are leveraging .ChildAdded instead of .Value so each node is read in one at a time - if the distance is not what we want, we can ignore it and move on to the next.
