In one of my controllers, a method returns a DataObjectSet of plain objects. Lets say the objects' class has a method called objectMethod that returns a value. In the template, I loop through the DSO with with <% control %> and print the value of objectMethod with $objectMethod. However it doesn't print. The template documentation says that $obj->objectMethod() should have been called. Fields work fine. What's happening?

Might be helpful if you post the affected code :D

Cart.php:

class Cart {
    var $_items = array(); // array of Cart_Items
    
    ...
    
    function getItems() {
        return new DataObjectSet($this->_items);
    }
}

class Cart_Item {
    var $_id;
    
    function getSubtotal() {
        return 0; // for testing
    }
}

class Cart_Controller extends Controller {

    ...
    
    function getItems() {
        return $this->_cart->getItems(); // $this->_cart is an instance of Cart
    }

}

Cart.ss:

<% control getItems %>
$getSubtotal // doesn't work
$_id // works
<% end_control %>

I think it is because you are inside a control getSubtotal is another control try using $Top to break out of the controls varibles to the controllers top level functions, also it looks like getSubtotal should be in the Cart_Controller and retrieve the value from Cart_Items?

<% control getItems %>
$Top.getSubtotal // should work
$_id // must be a property of getItems ?
<% end_control %>

This is a common confusion with SilverStripe has got me once or twice

_id and getSubtotal are in Cart_Item. getSubtotal multiplies the price of an item with its quantity. getItems returns an array of Cart_Items. Shouldn't <% control getItems %> loop through the array of Cart_Items, in which I can call the properties and methods of each Cart_Item?

Hmm I guess you can do that the Cart I have wrote for SilverStripe uses the SessionID in the Cart table and you call the getSubTotal from the Cart object (you could also do this with SQL and have a field to store it in the Cart DataObject)

Cart.php (dataobject)

...

public function getSubTotal()
	{
		$items = self::getBySessionID(session_id());
		$out = array();
		if($items) {
			foreach($items as $item) {
				array_push($out, ($item->Price * $item->Quantity));
			}
			return array_sum($out);
		}
	}

public function getBySessionID($SessionID)
	{
		return DataObject::get("Cart", sprintf("SessionID = '%s'", $SessionID));
	}
...

page.php (want these functions global)
Page_Controller

...

public function CartItems()
{
		$items = Cart::getBySessionID(session_id());
		return $items;
}

public function SubTotal()
{
		return number_format(Cart::getSubTotal(), 2);
}

...

Cart.ss (template include)

<table width="213" cellpadding="2" cellspacing="0">
  <% if CartItems %>
  <tr>
    <th align="left" class="borderleft">Product</th>
    <th align="left">Price</th>
    <th align="center">Qty</th>
    <th align="right">Total</th>
    <th align="right">&nbsp;</th>
  </tr>
  <% end_if %>
  <% if CartItems %>
  <% control CartItems %>
  <tr>
    <td class="borderleft"><a href="$Product.URLSegment/">$Product.Title</a></td>
        <td>$Product.Price</td>
        <td align="center"><form action="$Top.URLSegment/update" method="post"><div><input name="Quantity" class="quantity" value="$Quantity" size="1" maxlength="2" /><input type="hidden" name="CartID" value="$ID" /></div></form></td>
    	<td align="right">$Total</td>
        <td align="center"><a href="$Top.URLSegment/remove/$ID">x</a></td>
      </tr>
  <% end_control %>
  <% else %>
  		<tr class="empty"><td class="noborder" colspan="5">Your cart is currently empty.</td></tr>
  <% end_if %>
  <% if CartItems %>
  <% if UseGST %>
  <tr>
    <td align="left" valign="bottom" class="noborder">&nbsp;</td>
    <td colspan="2" align="right" class="noborder">Sub Total</td>
    <td align="right" nowrap="nowrap" class="borderleft">$SubTotal</td>
    <td align="right">&nbsp;</td>
  </tr>
  <tr>
    <td align="left" valign="bottom" class="noborder">&nbsp;</td>
    <td colspan="2" align="right" class="noborder">GST</td>
    <td align="right" class="borderleft">$GST</td>
    <td align="right">&nbsp;</td>
  </tr>
  <% end_if %>
  <tr>
    <td align="left" valign="bottom" class="noborder">&nbsp;</td>
    <td colspan="2" align="right" class="noborder"><strong>Total</strong></td>
    <td align="right" class="borderleft"><strong>$$GrandTotal</strong></td>
    <td align="right">&nbsp;</td>
  </tr>
  <% end_if %>
</table>

This seems to work well enough is probally a more pure SS way though hope this helps.

Thanks for the code, but I think there is a larger, more serious, problem.

The following test case does not work:

Test.php

class Apple {

	var $_color;

	function __construct($color) {
		$this->_color = $color;
	}

	function getColor() {
		return $this->_color;
	}
}

class Test_Controller extends Controller {
	function init() {
		parent::init();
	}

	function getApples() {
		$a = array();
		$a[] = new Apple('red');
		$a[] = new Apple('green');

		return new DataObjectSet($a);
	}
}

Test.ss:

<% control getApples %>
$_color // prints red and green
$getColor // does not print anything
<% end_control %>

You might have to use them statically depends on the way SilverStripe initializes the functions if it is statically then __construct may not be called you would have to do the new Apple('red') as this calls the constructor. So I am guessing SS is calling it like Apple::getColor()