update.rb

#Ruby
def self.new_from_db(row)
  new_student = self.new(row[1],row[2])
  new_student.id = row[0]
  new_student
end

def self.find_by_name(name)
  sql = "SELECT * FROM users WHERE name = ?"

  DB[:conn].execute(sql,name).map do |row|
    self.new_from_db(row)
  end.first
 end

def update
 sql = "UPDATE users SET name = ?, age = ? WHERE id = ?"
 DB[:conn].execute(sql, self.name, self.age, self.id)
end

tom = user.find_by_name("Tom")
tom.name = "Tommy"
tom.update

#Active Record
user = User.find_by(name: 'David')
user.update(name: 'Dave')