Rails 3 using fields_for in view doesn't work - ruby-on-rails

Question

I'm trying to implement master detail in a rails form with fields_for.
I have one model called Recipe:
class Recipe < ActiveRecord::Base
validates :name, :presence => true
validates :directions, :presence => true
has_many :recipe_ingredients
end
and one model called RecipeIngredient:
class RecipeIngredient < ActiveRecord::Base
belongs_to :recipe
#belongs_to :ingredient
end
In the new controller I populate the ingredients with three empty records like this:
def new
#recipe = Recipe.new
3.times {#recipe.recipe_ingredients.build}
# #ingredients = RecipeIngredient.new
respond_to do |format|
format.html # new.html.erb
format.xml { render :xml => #recipe }
end
end
What I would like to do in the view is to output the recipes fields (which works ok) and the three fields for recipe ingredients. In the top part of the view I have this:
<%= form_for :rec do |f| %>
I then list the recipe fields which are displayed correctly, like:
<div class="field">
<%= f.label :name %><br />
<%= f.text_field :name %>
</div>
I then try to display the ingredient lines but the code never seems to go into the fields_for section:
first try:
<% for ingredient in #recipe.recipe_ingredients %>
This prints out three times
<% fields_for "...", ingredient do |ingredient_form| %>
But this never prints out
<p>
Ingredient: <%= ingredient_form.text_field :description %>
</p>
<% end %>
<% end%>
I have three empty lines in recipe_ingredients and the for loop seems to iterate three times but the code within fields_for never triggers.
Second try:
<% for recipe_ingredient in #recipe.recipe_ingredients %>
b
<% fields_for "...", recipe_ingredient do |recipe_ingredient| %>
Rec: <%= recipe_ingredient.text_field :description %>
<% end %>
<% end %>
Third try (based on the answer here):
<% form_for :recipe do |f| %>
<% f.fields_for ingredients do |ingredient_form| %>
<p>
Ingredient: <%= ingredient_form.text_field :description %>
</p>
<% end %>
<% end %>
Is there something obvious I'm doing wrong?

Answer 1

You should use <%= instead of <% when using form_for and fields_for
The correct code should look like this:
<%= form_for :recipe do |f| %>
<%= f.fields_for :ingredients do |ingredient_form| %>
<p>
Ingredient: <%= ingredient_form.text_field :description %>
</p>
<% end %>
<% end %>

Answer 2

Switch it up to
<% form_for :recipe do |f| %>
<% f.fields_for :ingredients do |ingredient_form| %>
<p>
Ingredient: <%= ingredient_form.text_field :description %>
</p>
<% end %>
<% end %>