Rails嵌套形式：f.input和input（f）的区别

Question

I doing some forms, and tried to made a nested form that way:

<%= form_for(@birth) do |f| %>
    <%= f.text_area(:obs) %>
    <%= f.fields_for :child_attributes do |ff| %>
        <%= text_field(:child_attributes, :earring) %>
    <% end %>
<% end %>

Then, in BirthsController, I can get the nested attributes that way:

child = params[:child_attributes]

But, if I change my nested form to:

<%= form_for(@birth) do |f| %>
    <%= f.text_area(:obs) %>
    <%= f.fields_for :child_attributes do |ff| %>
        <%= ff.text_field(:earring) %>
    <% end %>
<% end %>

It does not work. What's exactly the difference between them, and why the second way (that I think is more elegant) do not work?

Thanks

Answer 1

The text_field method knows nothing about your object @birth , so the name of the field will just be child_attributes , that's why you can access it via params[:child_attributes] , but that's not what you want.

You should use ff.text_field . Then in your Birth model, add:

accepts_nested_attributes_for :child_attributes
attr_accessible :child_attributes_attributes