我想从产品编辑页面中删除“上传图片”和“浏览图片”按钮

Question

我正在尝试添加acl权限以允许/停止用户添加图片。我有acl部分工作。我只需要知道如何从块中删除按钮。

我在观察员中试过这个：

// get the block we are working with
$block = $observer->getBlock();

// if the block is null, there is no need to go any further
if( $block === null ) { return $this; }

if( $block instanceof Mage_Adminhtml_Block_Media_Uploader ) {

    if( ! Mage::getSingleton('admin/session')->isAllowed('catalog/products/edit_product_button') ) {
        // I tried this too
        // $block->unsetChildren();

        $block->unsetChild('browse_button');
        $block->unsetChild('upload_button');
        $block->unsetChild('delete_button');
    }

}

我已刷新缓存和缓存存储，按钮仍在显示。我做错了什么？