Swift & Vapor/Fluent : How to pull values from another table during a post router request

Question

I'm writing a backend app in Xcode 11.2 using Vapor3 and Fluent with SQLite . I have a route for a POST request to update a record in Table1, but before I save the record, I need to pull values from another table with a key that's in one of the fields I'm passing in. The part that I'm getting stuck on is accessing that data from the other table.

What I have so far:

Table for staff

final class Staff: Content, SQLiteUUIDModel, Migration, Parameter { 
  var id: UUID? 
  var staffID: String (value that's in the other table to match)
  var value1: Int (one of the values I'm trying to fetch)
  var value2: Int (another value I'm trying to fetch)
  ...(additional variables and Init

Table for assignments

final class Assignments: Content, SQLiteUUIDModel, Migration, Parameter {
  var id: UUID?
  var staffID: String 
  ...(additional variables and Init

Route for incoming POST request to update existing Assignment:

router.post("update", Assignments.parameter) { req -> Future<Assignments> in
  return try req.parameters.next(Assignments.self).flatMap { Assignment in
  return try req.content.decode(Assignments.self).flatMap { updatedAssignment in

  (Code where I perform calculations on the incoming 'Assignment' and save to 'updatedAssignment' before calling:)

  return WorkOrder.save(on: req)

The route I have works, incoming data is modified and written to the SQLite database, however there are a couple of fields that I need to perform calculations on or set to values stored in the Staff table. IE:

editedAssignment.variable = (variable) * (value1 from staff table for matching staffID)
editedAssignment.variable = (value2 from staff table for matching staffID)

What I've tried so far

let staffData = Staff.query(on: req).filter(\.staffID == staffID).all() before the calculations
(adding as a Future as:)
router.post(...) { req -> Future<Staff> in return try Staff.query(on: req).filter ...(rest of query)  

-- this method throws off the whole request, the values of the incoming request are just lost.

Ideally, if I could call a query and save as a dictionary in the calculations, that would be ideal, I just can't seem to "figure it out".

Answer 1

You need to put it inside your route, so that it is part of the chain, rather than disjointed as you had it:

router.post("update", Assignments.parameter) {
    req -> Future<Assignments> in
    return try req.parameters.next(Assignments.self).flatMap {
        assignment in
        return try req.content.decode(Assignments.self).flatMap {
            updatedAssignment in
            return Staff.query(on: req).filter(\.staffID == staffID).first().flatMap {
                staffData in 
                /* Code to update 'updatedAssignment' */
                return WorkOrder.save(on: req)
            }
        }
    }
}

You will most likely get compiler errors and need to put explicit return types in, but I can't predict/test these. I've left it in, but I don't think it is a good idea that you are explicitly stating a Future<Assignments> is being returned when you end up with the return from WorkOrder.save... .