#Here goes the description of what happens, below is the related code#I edit User (with habtm on Program) and validates_presence_of :programs but, even when the validation is triggered, the join table#gets inconsistent:-> Original table:mysql> select user_id,program_id,logname,p.name from programs_users pu,users u, programs p where user_id = u.id and program_id = p.id;+---------+------------+----------+------+| user_id | program_id | logname | name |+---------+------------+----------+------+| 2 | 2 | iherrera | SIT |+---------+------------+----------+------+1 row in set (0.00 sec)-> Create a new usermysql> select user_id,program_id,logname,p.name from programs_users pu,users u, programs p where user_id = u.id and program_id = p.id;+---------+------------+----------+------+| user_id | program_id | logname | name |+---------+------------+----------+------+| 2 | 2 | iherrera | SIT || 3 | 1 | Bar | SAT |+---------+------------+----------+------+-> Edit the user and remove all programs, I get validation error but the table gets hit anyway!!1 error prohibited this user from being savedThere were problems with the following fields: * Programs cant be blankbutmysql> select user_id,program_id,logname,p.name from programs_users pu,users u, programs p where user_id = u.id and program_id = p.id;+---------+------------+----------+------+| user_id | program_id | logname | name |+---------+------------+----------+------+| 2 | 2 | iherrera | SIT |+---------+------------+----------+------+1 row in set (0.01 sec)#Models related in habtm#$ more app/models/user.rbclass User < ActiveRecord::Base has_and_belongs_to_many :programs validates_presence_of :programsend#$ more app/models/program.rbclass Program < ActiveRecord::Base belongs_to :project has_and_belongs_to_many :users validates_presence_of :name, :project_id validates_presence_of :project, :message => "does not exist"end#Controller # POST /users # POST /users.xml def create prog_ids = params[:user][:programs] params[:user].delete(:programs) @user = User.new(params[:user]) @user.programs = [] if prog_ids != nil then prog_ids.each do |pi| @user.programs << Program.find(pi) end end respond_to do |format| if @user.save flash[:notice] = 'User was successfully created.' format.html { redirect_to(@user) } format.xml { render :xml => @user, :status => :created, :location => @user } else format.html { render :action => "new" } format.xml { render :xml => @user.errors, :status => :unprocessable_entity } end end end # PUT /users/1 # PUT /users/1.xml def update @user = User.find(params[:id]) prog_ids = params[:user][:programs] params[:user].delete(:programs) @user.programs = [] if prog_ids != nil then prog_ids.each do |pi| @user.programs << Program.find(pi) end end respond_to do |format| if @user.update_attributes(params[:user]) flash[:notice] = 'User was successfully updated.' format.html { redirect_to(@user) } format.xml { head :ok } else format.html { render :action => "edit" } format.xml { render :xml => @user.errors, :status => :unprocessable_entity } end end end