Flowering Chives Still Okay to Use?

All my chives I planted last year came back really good, but they have purple flowers on. Does that mean they went to seed or are they ok?

The regular onion chives, Allium schoenoprasum, has purple flowers which generally appear starting from the second year. This is normal, and does not mean that your plants are no longer usable (unlike some other herbs and veggies). However, you may have noticed that the stalk of the chives flowers is tough and quite inedible compared to the tender leaves. The leaves are what is used and you can always find a good supply of them in any clump of chives in flower. If you want to encourage more leaf production, you can remove the flowering stalks as they appear.
It is worth mentioning that the flowers are wonderfully edible too. If you gather them early, i.e., soon after they open, the flower heads can be pulled apart into the component flowers. Those flowers can be sprinkled on salads, omelettes, and egg dishes for both colour and flavour. It is important to gather the flowers early for this purpose because within days of the flowers opening the hard seeds develop making the flowers inedible.