/* Original code */
(…)
//	local price = AIEngine.GetPrice(engine);
//	if (HasMoney(price)) GetMoney(price);
//	local vehicle = AIVehicle.BuildVehicle(best_hangar, engine);
//	RepayLoan();
//	if (!AIVehicle.IsValidVehicle(vehicle)) {
//		if (!silent_mode) AILog.Error("Couldn't build the aircraft");
//		return -1;
//	}
(…)


/* Modified code */
class BuildVehicleMoneyTest {
    function DoMoneyTest(engine) {
		local price = AIEngine.GetPrice(engine);
	    if (WrightAI.HasMoney(price)) WrightAI.GetMoney(price);
	    local vehicle = DoBuildVehicle();
	    WrightAI.RepayLoan();
		if (!AIVehicle.IsValidVehicle(vehicle)) {
//		    if (!silent_mode) AILog.Error("Couldn't build the aircraft");
		    return null;
	    }
		return vehicle;
	}
}

class TestBuildVehicle extends BuildVehicleMoneyTest {
    h = null;
	e = null;
	
	function DoBuildVehicle() {
	    return AIVehicle.BuildVehicle(h, e);
	}
	
	function TryBuild(best_hangar, engine) {
	    h = best_hangar;
		e = engine;
		return DoMoneyTest(e);
	}
}

/* Somewhere else */
(…)
	local tvb = TestBuildVehicle();
	local vehicle = tvb.TryBuild(best_hangar, engine);
	if (vehicle == null) {
	    if (!silent_mode) AILog.Error("Couldn't build the aircraft");
		return -1;
	}
(…)