Rails yield - content_for problem

I have the following requirement.

Ex: There is a transaction table where it has columns say, transaction_name and amount. I want to loop through the transactions and display their details (transaction_name and amount) and finally I want to display the total amount (sum of all the amounts) in the head (before the loop) section of my page. (Think about it as a summary display)

Example page structure would be like

Sum of all the transactions - 200

transaction amount trn1 100 trn2 50 trn3 50

And I tried to use yield and content_for tag but no luck.

my code is as follows (i'm calling inside my erb file.)

<%= yield :transaction_summary %> 

<table>
  <% total_amount = 0%>
  <%for transaction in @transactions%>
    <tr>
      <td><%= transaction.transaction_name %></td>
      <td><%= transaction.amount %></td>
      <% total_amount += transaction.amount %>
    </tr>
  <%end%>
  </table>

<% content_for :transaction_summary do %>
   <h1>
     Sum of all the transactions - <%= total_amount %>
   </h1>
<% end %>

And

I'm using with inside a view (not inside a layout)

I'm using rails 2.2.2

Please help me and let me know if there is a better way

thanks in advance

cheers

sameera

EDIT:

Actually what I want to do is , Display some details before a particular loop where those details can be collected after the loop

Ex: If i have an array of transaction objects, I want to show a count of pass and failed transactions before the transactions loop in my view

thanks

I think you have the wrong idea about content_for and yield. :) http://guides.rubyonrails.org/layouts_and_rendering.html

   <h1>
     <%= @transactions.collect(&:amount).sum -%>
   </h1> 
   <table>
      <%for transaction in @transactions%>
        <tr>
          <td><%= transaction.transaction_name %></td>
          <td><%= transaction.amount %></td>
        </tr>
      <%end%>
    </table>

edit -

Regarding collecting data, I suggest you put them in helper methods:

#transactions_helper.rb
def transactions_total transactions
  @transactions_total ||= @transactions.collect(&:amount).sum
end

def passed_transactions transactions
  @passed_transactions ||= @transactions.collect{|transaction| transaction.passed == true}
end

def failed_transactions transactions
  @failed_transactions ||= transactions - passed_transactions(transactions)
end

Just noticed your comment to theTRON. The whole dry principle doesn't really apply to executing tiny logic such as looping through a array.