It makes sure that the field name argument is not empty, and that the field specified there is an actual existing field in the class which declares the method decorated with this attribute.
If you decorate something, you make it more attractive by adding things to it. He decorated his room with pictures of all his favorite sports figures Use shells to decorate boxes, trays, mirrors or even pots
If you decorate a room or the inside of a building, you put new paint or wallpaper on the walls and ceiling, and paint the woodwork. When they came to decorate the rear bedroom, it was Jemma who had the final say The boys are planning to decorate when they get the time I had the flat decorated quickly so that Philippa could move in. + decorating deco·rat·ing I did a lot of the decorating myself. + decoration deco·ra·tion The renovation process and decoration took four months
To deck with that which is becoming, ornamental, or honorary; to adorn; to beautify; to embellish; as, to decorate the person; to decorate an edifice; to decorate a lawn with flowers; to decorate the mind with moral beauties; to decorate a hero with honors
If someone is decorated, they are given a medal or other honour as an official reward for something that they have done. He was decorated for bravery in battle
{f} ornament; adorn; make beautiful; bestow a medal or honor on someone (e.g. in the armed forces)