Math with table rows

Lets supose I have a User table, and on this table I have height, weight and result rows.

In a form I input height and weight values and want to multiply those two values and store on the resulta row on database. I was trying something like that

def criar

@user =[:user])

@result = @user.height * @user.weight

@user.result = @result

But its not working, what am i doing wrong?

What does "not working" mean?

You should be doing this in the model, not controller.

If you want to do this everytime the user record is saved, then define a before_save callback in your model and add this in the method

def udpate_result

self.result = self.height*self.weight


Note: You will have to convert height and weight to integer/float if you have not defined those columns as just string in the database.