What is the best way to handle nested futures? - fluent

Question

I have users and groups in my system. Users belong to groups using a sibling relationship. I need to transform the Users/Groups into an Array of users/groups to return to the client. When I lookup a user I get a Future, if I then map the use and attempt to access its groups I get a Future.
What is the best way of handling nested futures so I can get to the actual data and munge it?
struct ReturnUserStruct {
var userId: Int
var primaryGroupName: String
}
let futureUsers = Users.query(on: request).all()
futureUsers.map { users in
var returnUsersArray<returnUserStruct> = []
users.ForEach { user in
var returnUserStruct: ReturnUserStruct
returnUserStruct.userId = user.id
// This a sibling relationship that returns a Future
primaryGroupFuture = user.primaryGroup
primaryGroupFuture.map { group in
returnUserStruct.primaryGroupName = group.name
}
returnUsersArray.append(returnUserStruct)
}
return returnUsersArray
This code doesn't work. The map call are obviously scheduled asynchronously and returnUsersArray ends up empty. I can rearrange this and get the user ids into the return array but haven't figured out a good way to get the groupName.

Answer 1

Good to hear about Fluent4 and Vapor4. Here is the solution I've settled on.
return Users.query(on: request)
.all()
.and(Group.find(user.primaryGroup).first())
.map { (users, groupOptional) -> [ReturnUserStruct]
guard let group = groupOptional else {
Abort(.notFound)
}
var returnArray: Array<ReturnUserStruct>
users.forEach { user in
var returnUserStruct: ReturnUserStruct
returnUserStruct.userId = user.id
returnUserStruct.primaryGroupName = group.name
returnArray.append(returnUserStruct)
}
}
It seems to work, here's hope .and sticks around.
Thanks