not working w/ page caching, works with block, css, js caching

Unfortunately, Ubercart must be patched for this (I plan to provide the patch to Ubercart maintainers). Cart block must know whether page caching is turned on. For now, it performs this check (line 406 of uc_cart.module):
$cachable = !$user->uid && variable_get('cache', CACHE_DISABLED) != CACHE_DISABLED;
You can add the following line:
if ((module_exists('ajaxblocks')) && (ajaxblocks_in_ajax_handler())) $cachable = FALSE;

Hope it'll help.

With the following fragment of uc_cart.module:

        $cachable = !$user->uid && variable_get('cache', CACHE_DISABLED) != CACHE_DISABLED;
        if ((module_exists('ajaxblocks')) && ((ajaxblocks_in_ajax_handler()) || ($_SERVER['REQUEST_METHOD'] == 'POST'))) {
          $cachable = FALSE;
        }
        $uc_cart_path = drupal_get_path('module', 'uc_cart');

and normal caching mode and block caching everything works as expected for me. Did you set the setting 'Load block via AJAX' to 'yes' for the cart block?

Checking $_SERVER['REQUEST_METHOD'] == 'POST' is not quite correct, but you can use it now.

I'm having the same problem. Although I have other blocks working fine (a mini cart block showing only the cart total), the cart block is not showing anything for the anonymous.

Page cache set to normal, block caching enabled and cart block setting for "Load block via AJAX" set to YES.

I've also tried to use the cache excludes module to exclude all ajax* urls, but with no luck again.

Finally I've also tried to use this module with boost, but then it doesn't seem to do anything of its magick. The blocks are been displayed (and cached) directly on the page. Is it compatible with boost?

*** EDIT ***
The first issue seems to be corrected after some custom javascript incompatibility has been corrected.

And just figured out how to make this work with boost.
On Boost settings page, the "Boost - Static page cache:" must be on "(Not Recommended) Set Boost & Core (if enabled) cache for each page".

@miraclegr, could you clarify your situation? Do you use unpatched (by patch in comment #4) Ubercart?
If you need just simple cart block, I can suggest http://drupal.org/project/uc_microcart module which works fine with ajaxblocks.
And, as much more complicated solution, http://drupal.org/project/uc_ajax_cart may be used. It really loads cart block via ajax when anonymous caching is on (you don't need ajaxblocks for this). I have working example here: http://www.igrushkispb.ru

I didn't try ajaxblocks with Boost. Do you think it's actual combination, and the solution should be documented in README of ajaxblocks?

I'm using patched version of ubercart. Haven't tried it without the patch though to be honest.
The problem I had was not with the modules I use, but some custom javascript that has been fixed now.
We have a microcart (custom code in block) and a normal cart block that displays when the user hovers on microcart. So they can see the contents of the cart without going to a different page.

The ajax cart was not chosen because, while it provides a nice working solution, I didn't want the Add to cart button to work with ajax. The reason is that some usability tests that we've done, showed us that the users (most of them) got confused with all these messages or didn't noticed them at all. They ended up adding more than once the product in the cart or just got frustrated and left.

Overall, because we use the ajaxblock for the microcart block, it is much better from the performance perspective to have all ajax blocks loaded with one call.

So the only workaround for us was to have the microcart and cart block loaded with ajax for anonymous users and keep the original add to cart functionality.

As for the Boost module, I can confirm that with the settings described earlier, it works fine. If you don't enable the core caching, the ajaxblocks module don't work at all.
I also have the authcache module installed, so new customers that complete the checkout process, get logged in and still get cached content (but without the ajax blocks this time).

I think that the part that needs to be in documentation is the settings you need (for different scenarios) so that users can get to work as expected very quickly.

Hope this helps

Thanks for the good work

@echoz, sorry, I didn't understand your situation.
Ajax Blocks can't work when "Hide block if cart is empty" is checked. If some block's content is empty, there will be no attempt to load it's context via AJAX afterwards. It's Drupal core (block.module) that makes this:

        if (isset($block->content) && $block->content) {
          // Override default block title if a custom display title is present.
          if ($block->title) {
            // Check plain here to allow module generated titles to keep any markup.
            $block->subject = $block->title == '<none>' ? '' : check_plain($block->title);
          }
          if (!isset($block->subject)) {
            $block->subject = '';
          }
          $blocks[$block->region]["{$block->module}_{$block->delta}"] = $block;
        }

So, no further processing is possible for empty blocks.

@maximpodorov I used your code snippet in #1 and it fixed my problem. Did you ever submit it to the UC maintainers?

@AndyF
No, the problem is more deep. I need some time to prepare a patch for Ubercart which will make it work without Ajaxblocks module (see #911052: Solution for AJAX loading of the cart).

Understood, thanks.

Just in case anyone wants the ubercart shopping cart with ajaxblocks, you can use this (real dirty) trick on top of the patch above.

1. Create a block template that just prints the block content for the shoping cart:

block-uc_cart-0.tpl.php

<?php print $block->content ?>

2. Tweak the theming functions for the shopping cart so they print the full block and some non printable stuff when the cart is empty:

function yourthemenamehere_uc_cart_block_content($help_text, $items, $item_count, $item_text, $total, $summary_links) {
  if ($item_count) {
    $output = '<div id="block-uc_cart-0" class="block block-uc_cart">';
    $output .= '<h2 class="title">' . theme_uc_cart_block_title('Su compra' , 'cart-block-icon-full', TRUE). '</h2>';
    $output .= '<div class="content">';
    $output .= theme_uc_cart_block_content($help_text, $items, $item_count, $item_text, $total, $summary_links);
    $output .= '</div></div>';
    return $output;
  }
  else {
    // This will trick the block system into displaying the block though it is actually empty.
    return '&nbsp';
  }
}

function yourthemenamehere_uc_cart_block_title($title, $icon_class = 'cart-empty', $collapsible = TRUE) {
  return '';
}

Have fun!

Outstanding, suggestion #1 worked for me in D7, Ubercart 7.x-3.0-beta3, although the line # was different. I placed it after line #342 (in uc_cart.module)as follows:

if ($delta == 'cart') {
    $cachable = !$user->uid && variable_get('cache', 0);
	if ((module_exists('ajaxblocks')) && (ajaxblocks_in_ajax_handler())) $cachable = FALSE;
    $product_count = count(uc_cart_get_contents());

    // Display nothing if the block is set to hide on empty and there are no
    // items in the cart. 

Thank yo so much Max!