How to avoid having.uveitis if i have ra and if occured does it have a cure?

No prevention: There is no known prevention of uveitis in those prone to get it. All you can do is see an ophthalmologist asap should you have redness, pain or sensitivity to light.

Control your RA: Is the best advice. Yes it is treatable if you get it but i wouldn't call it a "cure".

Awarenes of sympoms: Most rheumatic disease has a slightly higher risk of uveitis, especially anklyosing spondylitis. There is nothing you can do to prevent its occurrence should it want to arise, although some think treating the arthritis lowers the risk. Be aware of the light sensitivity, redness and pain which are the hallmarks of this condition so you can get treated if it happens.