gistfile1.rb

class TasksController < ApplicationController
  def create
    @task = Task.new(params[:task])
    respond_to do |format|
      # If all is well, clear out the new_task store and redirect to the project
      if @task.save
        session[:new_task] = nil
        flash[:notice] = 'Task added successfully'
        format.html { redirect_to @task.project }
      # If something goes south, save the task that is being worked on
      else
        session[:new_task] = @task
        format.html { redirect_to @task.project }
      end
    end
  end

  # other actions...
end

class ProjectsController < ApplicationController
  def show
    @project = Project.find(params[:id])
    # don't want to accidentally display the task that is being worked on
    @old_shifts = @project.tasks.delete_if {|s| s.new_record?}
    # If we are already working on a task in the store, use that, otherwise instantiate a new one
    @new_task = session[:new_task] || Task.new(:project_id => @project.id)

    respond_to do |format|
      format.html
    end
  end

  # other actions...
end