Getting a response from an Azure insert - azure-mobile-services

Question

I have inherited the development of an iOS app that connects to an Azure mobile service, and I'm stuck on getting an acceptable response from my insert operations. Specifically I want to get back the object that was inserted, or at least the value of its id field, from a Custom API script that the previous developer on this project created.
A truncated version of the Custom API script I'm using looks like:
exports.post = function(request, response) {
var mssql = request.service.mssql;
var sql = "INSERT INTO Reservation (<field names>)" +
" VALUES (<field values>); "
+"SELECT id FROM Reservation WHERE __updatedAt = (SELECT MAX(__updatedAt) FROM Reservation);";
mssql.query(sql, {
success: function(results) {
console.log("after post - results = " + results);
response.send(statusCodes.OK, results);
}
});
};
When I run the iOS app and post a Reservation (using the AFNetworking class to communicate with the server), I get back a response object with an empty array. Furthermore, inspecting the Azure log for the results of the console.log statement in my function, I see two results: "after post - results = [object Object]" and "after post - results =".
I'm clearly doing something wrong, but I don't understand what. I have tried a number of other different approaches, all with similarly unsatisfactory results. For what it's worth, the "get" script for this class works just fine. I wonder if anybody can help me get this "post" script right.

Answer 1

As you noted in your logs, the success callback for the mssql.query call is being called twice - since you have two statements in your query. When you first call response.send, that's the response which is sent back to the client. The first callback will contain the results for the INSERT call, which is not what you want to return. You should use a flag to indicate which result you're receiving, and only return if it's the one you want:
exports.post = function(request, response) {
var mssql = request.service.mssql;
var sql = "INSERT INTO Reservation (<field names>)" +
" VALUES (<field values>); "
+"SELECT id FROM Reservation WHERE __updatedAt = (SELECT MAX(__updatedAt) FROM Reservation);";
var firstCall = true;
mssql.query(sql, {
success: function(results) {
console.log("after post - results = " + results);
if (firstCall) {
firstCall = false;
} else {
response.send(statusCodes.OK, results);
}
}
});
};