why is code not executing on return from Future in Dart program - dart

Question

Could someone please explain to me why in the following code (using r25630 Windows), the value of iInsertTot at line 241 is null, or more to the point, why is line 234 ("return iInsertTot;") not executed and therefore at line 241, iInsertTot is null. The value of iInsertTot at lines 231/232 is an integer. While I can and probably should code this differently, I thought that I would try and see if it worked, because my understanding of Futures and Chaining was that it would work. I have used “return” in a similar way before and it worked, but I was returning null in those cases (eg. line 201 below).
/// The problem lines are :
233 fUpdateTotalsTable().then((_) {
234 return iInsertTot;
235 });
While running in the debugger, it appears that line 234 “return iInsertTot;” is never actually executed. Running from command line has the same result.
The method being called on line 233 (fUpdateTotalsTable) is something I am just in the process of adding, and it consists basically of sync code at this stage. However, the debugger appears to go through it correctly.
I have included the method “fUpdateTotalsTable()” (line 1076) just in case that is causing a problem.
Lines 236 to 245 have just been added, however just in case that code is invalid I have commented those lines out and run with the same problem occurring.
218 /*
219 * Process Inserts
220 */
221 }).then((_) {
222 sCheckpoint = "fProcessMainInserts";
223 ogPrintLine.fPrintForce ("Processing database ......");
224 int iMaxInserts = int.parse(lsInput[I_MAX_INSERTS]);
225 print ("");
226 return fProcessMainInserts(iMaxInserts, oStopwatch);
227 /*
228 * Update the 'totals' table with the value of Inserts
229 */
230 }).then((int iReturnVal) {
231 int iInsertTot = iReturnVal;
232 sCheckpoint = "fUpdateTotalsTable (insert value)";
233 fUpdateTotalsTable().then((_) {
234 return iInsertTot;
235 });
236 /*
237 * Display totals for inserts
238 */
239 }).then((int iInsertTot) {
240 ogTotals.fPrintTotals(
241 "${iInsertTot} rows inserted - Inserts completed",
242 iInsertTot, oStopwatch.elapsedMilliseconds);
243
244 return null;
245 /*
192 /*
193 * Clear main table if selected
194 */
195 }).then((tReturnVal) {
196 if (tReturnVal)
197 ogPrintLine.fPrintForce("Random Keys Cleared");
198 sCheckpoint = "Clear Table ${S_TABLE_NAME}";
199 bool tClearTable = (lsInput[I_CLEAR_YN] == "y");
200 if (!tFirstInstance)
201 return null;
202 return fClearTable(tClearTable, S_TABLE_NAME);
203
204 /*
205 * Update control row to increment count of instances started
206 */
207 }).then((_) {
1073 /*
1074 * Update totals table with values from inserts and updates
1075 */
1076 async.Future<bool> fUpdateTotalsTable() {
1077 async.Completer<bool> oCompleter = new async.Completer<bool>();
1078
1079 String sCcyValue = ogCcy.fCcyIntToString(ogTotals.iTotAmt);
1080
1081 print ("\n********* Total = ${sCcyValue} \n");
1082
1083 oCompleter.complete(true);
1084 return oCompleter.future;
1085 }

Answer 1

Your function L230-235 does not return anything and that's why your iInsertTot is null L239. To make it work you have to add a return at line 233.
231 int iInsertTot = iReturnVal;
232 sCheckpoint = "fUpdateTotalsTable (insert value)";
233 return fUpdateTotalsTable().then((_) {
234 return iInsertTot;
235 });