"Night-time Dryness".... is not attained, even until 7 years old. It is a Biological based occurrence. This is per our Pediatrician as well.
A mere 4 year old, cannot control their bladder when asleep. Punishing will not 'make' them not have accidents or to be dry.
It is biological based. Not him being naughty on purpose.
Here is a link, from Parents magazine, about bed-wetting Myths:
http://www.parents.com/toddlers-preschoolers/sleep/bed-we...
http://www.parents.com/kids/sleep/bed-wetting/bed-wetting...
http://www.parents.com/kids/sleep/bed-wetting/dr-alan-gre...
My daughter is 7 years old.... she still has occasional accidents. No biggie. My daughter was still using night diapers until she was already 5 years old. Her Kindergarten Teacher said, that MANY MANY kids that age or older, still have pee accidents at night and use night time diapers. But, the parents won't admit it. Because they feel peer pressure about it all... not knowing that biologically, night time bladder control and consciousness is not fully developed yet at that stage.
I just use for her and my son, a water proof bed pad under them.
My Husband, even when he was older than 7, would have occasional pee accidents at night.
Keep in mind, that a child WILL have accidents. They are not perfect.
Scolding them for it, will not work.
Night-time bladder ability is entirely different than daytime potty ability.
all the best,
Susan