Many gardeners have frustratingly tried growing eggplants to find that they have an abundance of the beautiful purple flowers and see NO harvest! In order for eggplants to self-pollinate, the plants need to be far enough apart for the wind to jostle the flowers so that the pollen can fall onto the pistil, pollinating the flower. This can also be a problem in very humid conditions, when the pollen is too sticky to go anywhere.
Fortunately, on the rooftop we have no shortage of wind, so our eggplants are in full production! If you're trying to grow eggplant and not sure that your plants will get enough wind, you can pollinate the flowers yourself by taking a clean paintbrush and moving it around inside of the flowers. This will ensure the pollen gets to the pistil.
Also, don't forget that eggplants like a lot of water - 2 inches a week, in fact. So if you're still having problems with flowers falling off before they fruit, try upping your watering and see if that helps.