Store ID's in has_many or habtm associated tables

In has_many or habtm association we sometime need to store array of id's.
So, this is how we do it.

table : Projects,  :Categories
Model: Project, Category

html form

    = f.select :category_ids, Category.all.collect{|p| [p.name, p.id]},{:include_blank => false, :prompt=>"select catgory" }, :multiple=>true

And in the controller maintain your normal flow.


def create
    if params
      @project = Project.create( params[:project])
      #@project.categories << params[:project][:category_ids]
      if @project.save
        flash[:success] = "Project created successfully"
        redirect_to :action=>"list"
        return
      else
        @project.screenshot = nil
        params[:project][:screenshot] = nil
        flash[:error] = @project.errors
      end
    end
    render :action=>"new"
end