How query works in Vapor? - filter

Question

How to return user if based on facebook user ID it already exist, and create a new user if not exist in Vapor? You can see how I tried fetch data, but get error.
final class User: Content {
var id: Int?
var fbId: String
init(id: Int? = nil, fbId: String) {
self.id = id
self.fbId = fbId
}
}
router.get("user") { (request) -> Future<User> in
return Future.map(on: request) { () -> User in
let fbId = try request.query.get(String.self, at: "fbId")
return User.query(on: request).filter(\.fbId == fbId).first().map { (user) -> (U) in
if user == nil {
user = User(fbId: fbId)
}
return user
}
}
}

Answer 1

You have a few things going on here. To start with you don't need the first Future.map - not sure what that's doing.
Then you have the issue of the compiler - you have to return the same type in each closure and the function, which is awkward because if you already have a user you can return that, if you don't you need to create and save one, which returns Future<User>, which is not the same to User.
So to answer your question, U there should be User, but really you want to change first().map to first().flatMap in which case U becomes Future<User>. Then you can do something like:
router.get("user") { req -> Future<User> in
let fbID = try req.query.get(String.self, at: "fbId")
return User.query(on: req).filter(\.fbId == fbID).first().flatMap { user in
let returnedUser: Future<User>
if let foundUser = user {
returnedUser = req.future(foundUser)
} else {
let newUser = User(fbId: fbID)
returnedUser = newUser.save(on: req)
}
return returnedUser
}
}
To solve your problems. Hope that helps!

Answer 2

.map { (user) -> (U) in
This defines that you get a user into the closure and have to return a U. In your example you want to return a User (so change U to User).
If you want to create the user (in case it is nil) you probably also want to store it in the database? If that's the case, you'll have to change map to flatMap and update like this:
.flatMap { (user) -> EventLoopFuture<User> in
if user == nil {
return User(fbId: fbId).save(on: req)
}
return req.future(user)
}