First, as a preventative, i wash fruits when they come in the hose to remove the fruit fly eggs. When I get them anyway, I leave the lid of my compost container ajar. When a bunch have congregated inside, I quickly snap the lid down, then take it outside. Even if I don't go all the way to the compost pile, the flies will depart when the lid is opened and not return to the house. It takes several tries, but works for me.