What is the name of a children's book about magic figs?

I read a book when I was younger about a man and his dog (he was not nice to the dog). When the man ate the figs his dreams that night would come true. So he concentrated on dreaming of being rich and owning a boat but before he could eat the figs the dog ate them and the dog dreamed that he and his master swapped bodies. I just can't remember the name of the book and can't find out anything about it...help :o)