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POHow do I access ActionView's fields_for index when iterating over many child records?
 

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  1. POHow do I access ActionView's fields_for index when iterating over many child records?
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    <p>I have a Rails 2.3.10 app that uses fields_for to include fields on a has_many association's attributes. I'm using accepts_nested_attributes_for on the the parent model and its many children are being shown in the form using:</p> <pre><code>&lt;% form_for :map do |f| %&gt; ... &lt;% f.fields_for :markers do |marker_f| %&gt; &lt;%= marker_f.text_field :lat &lt;%= marker_f.text_field :long &lt;% end %&gt; &lt;% end %&gt; </code></pre> <p>The fields_for helper iterates over the child marker models and the text_field inputs are generated for each. These text fields have generated id values like: </p> <ul> <li><p>map_markers_attributes_0_lat and map_markers_attributes_0_long </p></li> <li><p>map_markers_attributes_1_lat and map_markers_attributes_1_long</p></li> <li><p>...</p></li> <li><p>map_markers_attributes_5_lat and map_markers_attributes_5_long</p></li> </ul> <p>The integer in the id is an index of the records array being iterated over. How do I access this index value for use elsewhere in my code?</p> <p>For example I want to use Javascript to access the id values on these inputs. </p> <pre><code>&lt;% form_for :map do |f| %&gt; ... &lt;% f.fields_for :markers do |marker_f| %&gt; &lt;%= marker_f.text_field :lat &lt;%= marker_f.text_field :long &lt;% content_for :head do %&gt; &lt;% javascript_tag do %&gt; $('&lt;%= generate_html_id(marker_f, :lat) %&gt;').observe_field('change'); $('&lt;%= generate_html_id(marker_f, :long) %&gt;').observe_field('change'); &lt;% end %&gt; &lt;% end %&gt; &lt;% end %&gt; &lt;% end %&gt; </code></pre> <p>I insert some javascript into the head of the html to observe the field for any changes. I need to know the id of the field and my generate_html_id method should be able to replicate the id of the field from the marker_f builder object. However I don't know how to get the index value coming from fields_for.</p> <p>It seems like there should be a fields_for_with_index method but there is not:</p> <pre><code>&lt;% form_for :map do |f| %&gt; ... &lt;% f.fields_for_with_index :markers do |marker_f, i| %&gt; &lt;%= marker_f.text_field :lat &lt;%= marker_f.text_field :long &lt;% content_for :head do %&gt; &lt;% javascript_tag do %&gt; $('&lt;%= generate_html_id(marker_f, :lat, i) %&gt;').observe_field('change'); $('&lt;%= generate_html_id(marker_f, :long, i) %&gt;').observe_field('change'); &lt;% end %&gt; &lt;% end %&gt; &lt;% end %&gt; &lt;% end %&gt; </code></pre> <p>BTW I could create custom id values for the field but would prefer to stick to the conventions.</p>
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    1. COHaving not found any way to access the @auto_index on the fields_for iterator I've solved the immediate problem; I've just created my own index for the loop.
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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