When I was visiting some blogs about the home garden care. I read a question from a lady. She was asking about the egg plant. She was asking that she plant some egg plant and potatoes in her garden. They are grow healthy. They have flowers but there are no fruits. The egg plant and the potatoes are comes under the nightshade family. If you have the same problem, then here is the answer of your problem as well.
On August, it is very hot on the night and the temperature is high, and the plants are still warm. As soon as the temperature goes down, your plants will start producing the fruits, and you can use them as you want. However, you have to wait until the temperature is suitable for your plants. Do not use the nitrogen for the plants, or it will cause the inhabit to the plants, or maybe it reduces flowering.
This is happened because the plants will use the power in the growth of the new leaves rather than the fruits. Nightshade family plants contain nicotine like tobacco, but the level is less than the tobacco. In the 5th century, the Chinese women were using the egg plant to clean their teeth. They use the purple egg plant for the dying the skin.