How to stop my cupboard doors from swinging open

Depending on the age of the cabinet you could have a pin that meets a socket where the socket spring is worn. the next generation is a roller that has a spring with in it that hits a catch on the frame. The newest versions have a claw that catches a pin or a magnet. Lastly the hinge its self could have a spring in it to hold the door closed.

Depending on what you have the best solution is to replace with the same type. I would go to a local hardware store with the pieces of what you have now and try to get a newer set.

Sometimes the mounting points (screw holes) are worn or stripped out:

• With a wood cabinet and door you might be able to drill out the area and then using a hardwood dowel plug, glue the dowel in then sand down the area and repaint/finish as needed.
• In the case of a metal cabinet and door you'll need to find a larger screw or plastic screw plug that will fit into the hole or enlarge the hole carefully so it fits to support your current screw.

If you want to change out the catch I would go with a magnet type. The only problem here is they are not very strong so anything pressing against the door if over stuffed will pop it open unlike the mechanical models. Or if you can switch-out the hinges with the spring type that hold the door closed.