Practice: KelloggCoin Web – Solution

<!-- Step 1: List all transactions, starting with the ICO -->
<ol>
  <% for transaction in Transaction.all %>
    <% from_user = User.find_by({ "id" => transaction["from_user_id"] }) %>
    <% to_user = User.find_by({ "id" => transaction["to_user_id"] }) %>

    <li>
      <% if from_user %>
        <%= transaction["amount"] %> from <%= from_user["name"] %> to <%= to_user["name"] %>
      <% else %>
        Initial coin offering: <%= transaction["amount"] %> to <%= to_user["name"] %>
      <% end %>
    </li>
  <% end %>
</ol>

<!-- Step 2: Calculate and display the balances -->
<ul>
  <% for user in User.all %>
    <% 
      balance = 0
      balance = balance + Transaction.where({ "to_user_id" => user["id"] }).sum("amount")
      balance = balance - Transaction.where({ "from_user_id" => user["id"] }).sum("amount")
    %>

    <li>Balance for <%= user["name"] %>: <%= balance %> KC</li>
  <% end %>
</ul>

Alternatively, using a <table>:

<!-- Step 1: List all transactions, starting with the ICO -->
<table>
  <tr>
    <th>From User</th>
    <th>To User</th>
    <th>Amount</th>
  </tr>
  <% for transaction in Transaction.all %>
    <% from_user = User.find_by({ "id" => transaction["from_user_id"] }) %>
    <% to_user = User.find_by({ "id" => transaction["to_user_id"] }) %>
    <tr>
      <td>
        <% if from_user %>
          <%= from_user["name"] %>
        <% else %>
          Initial coin offering
        <% end %>
      </td>
      <td><%= to_user["name"] %></td>
      <td><%= transaction["amount"] %></td>
    </tr>
  <% end %>
</ol>

<!-- Step 2: Calculate and display the balances -->
<table>
  <tr>
    <th>User</th>
    <th>Balance</th>
  </tr>

  <% for user in User.all %>
    <% 
      balance = 0
      balance = balance + Transaction.where({ "to_user_id" => user["id"] }).sum("amount")
      balance = balance - Transaction.where({ "from_user_id" => user["id"] }).sum("amount")
    %>

    <tr>
      <td><%= user["name"] %></td>
      <td><%= balance %> KC</td>
    </tr>
  <% end %>
</table>