has_many build method, Rails

Question

Another newbie question.

The goal: each ingredient can have zero or more unit conversions tied to it. I want to put a link to creating a new unit conversion on the page

Answer 1

Unit Conversion Controller for new and create should be:

def new
  @ingredient = Ingredient.find(params[:ingredient_id])    
  @unit_conversion = @ingredient.unit_conversions.build
end

def create
  @ingredient = Ingredient.find(params[:ingredient_id])    
  @unit_conversion = @ingredient.unit_conversions.build(params[:unit_conversion])

  if @unit_conversion.save
    flash[:notice] = "Successfully created unit conversion."
    redirect_to ingredient_unit_conversions_url(@ingredient)
  else
    render :action => 'new'
  end
end

Also, this screencast is a nice resource for nested resources.