CRJ-700 First Officer reported that a #2 IDG failure caused a flap malfunction due to load shedding. After the APU generator came back online; the flaps operated normally and the flight crew continued to the destination airport and made a precautionary landing.

Narrative

Enroute to ZZZ; just prior to descent; three caution messages appeared: HYD Press Low; flap fail; [and] something else related to hydraulics - resolved before QRHed. Multiple status messages appeared as well; mostly related to TRUs (Transformer Rectifier Units). After running the QRH for the hydraulic pressure; the only caution message remaining was for flap fail and the electric status messages. The status messages were run according to the QRH and non-messages" were referenced. All synoptic pages were consulted and the only noticeable anomaly was the loss of generator attached to Engine 2; RH. No caution messages of a generator failure appeared.Per procedure; the flap fail QRH was run and plans for a flaps up landing; no slat failure were made; including [requesting priority handling] with ATC. ACARS was not operational. Out of an abundance of caution; the APU was started during descent. After the APU generator was engaged; the flap fail message disappeared. The electrics synoptic page did not visually show a power transfer except for the KVA load; which indicated some use of the APU generator. Flaps were then able to be deployed for landing; but the [priority handling] status was maintained for safety. The aircraft was dispatched with a "flap half speed" MEL for the flight and multiple previous others. Flight attendants were not asked to brace; landing was otherwise normal; and aircraft taxied to gate under own power."