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I have a buildings database with a user table, who can have multiple buildings. I have written a route which receives a user id and sends back details of all the buildings that are registered to that user. Response includes Buildings -> Floors -> Rooms.

Debugging the code gives me valid data returning on every query, but the final response is always null. I know there is some asynchronous issue here, can't seem to figure out the solution. 

    var rooms = []
    var buildings_info = { Buildings:[] }
    var floor_response = { Floors: [] }

    var query = "Select Building_Id, Building_Address from Buildings WHERE ?? = ?";
    var table = ["User_Id", user_id];
    query = mysql.format(query, table);

    connection.query(query, function(error, data){

        for(let k=0; k<data.length; k++)
        {

            floor_response = { Floors: [] }

            var query2 = "Select Floor_Id, Floor_Name from Floors WHERE ?? = ?";
            var table2 = ["Building_Id", data[k].Building_Id]

            query2 = mysql.format(query2, table2);

            connection.query(query2, function(error, data2){
                for(let l=0; l<data2.length; l++)
                {
                    var room_response = { Rooms : [] }

                    var query3 = "Select Room_Id, Room_Name from Rooms where ?? = ?";
                    var table3 = ["Floor_Id", data2[l].Floor_Id]

                    query3 = mysql.format(query3, table3);

                    connection.query(query3, function(error, data3){

                        for(let m=0; m<data3.length; m++)
                        {
                            debug("for 3: "+data3[m].Room_Name)
                            room_response.Rooms.push({"Room_Id":data3[m].Room_Id, "Room_Name":data3[m].Room_Name})
                            debug("Rooms Data: "+JSON.stringify(room_response))
                        }
                    })

                floor_response.Floors.push({"Floor_Id":data2[l].Floor_Id, "Floor_Name":data2[l].Floor_Name, "Rooms":room_response})
                }

            })
            buildings_info.Buildings.push({"Building_ID":data[k].Building_Id, "Building_Address":data[k].Building_Address, "Floors":floor_response})
        }
reply({"Buildings":buildings_info})
Zaid Waseem
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  • You're calling reply before any query callbacks have run. `buildings_info.Buildings` is empty because you haven't put anything in it yet. Call reply after all the queries are done instead. – Paul Mar 22 '19 at 07:35
  • Since you have a query in a loop you'll probably also want to look at something like this: https://stackoverflow.com/questions/18983138/callback-after-all-asynchronous-foreach-callbacks-are-completed – Paul Mar 22 '19 at 07:38

0 Answers0