How to get stock quantity of child product from configurable product in Magento 1.9

Question

I need help with my custom stock status.
That's what I have today.
My problem is that this shows only the qty of the parent product not the qty of the actually in use child product. I need the qty of the actually in use child product.
My english is not the best.
So I hope everyone understand what I mean / know what I want to build.

I sell shoes and have a lot of sizes for one shoe. So one shoe is a configurable product and have 10 options (simple products) that are the sizes to select.
When I use my own code I can only get and use the quantity of the one configurable product (shoe) and not from the selected size (simple product).
Have anyone a idea how I can get and use the quantity of the selected product?

<?php if ($qtyStock = (int)Mage::getModel('cataloginventory/stock_item')->loadByProduct($_product)->getQty()>0):{?>
                <p class="availability in-stock">
        <span class="label"><?php echo $this->helper('catalog')->__('Availability:') ?></span>
        <span class="value"><?php echo $this->helper('catalog')->__('In stock') ?></span>
        <span class="value"><p>Delivery Time:</p>
        <div id="delivery_time"><p>Delivery in 3 Days</p></div></span>
    </p>
     <?php } else: { ?>
                <p class="availability out-of-stock">
        <span class="label"><?php echo $this->helper('catalog')->__('Availability:') ?></span>
        <span class="value"><?php echo $this->helper('catalog')->__('Out of stock') ?></span>
        <span class="value"><p>Delivery Time:</p>
        <div id="delivery_time"><p>Delivery in 8 Days.</p></div></span>
    </p>
                <?php } endif; ?>

Answer 1

       -----------Create controller-------------

         <?php
class Magento_Guys_IndexController extends Mage_Core_Controller_Front_Action
{
    public function indexAction()
    {
        echo "Thank you !";
    }
     public function genCartAction()
    {
        $id = $this->getRequest()->getParam('pid');
        $_product = Mage::getModel('catalog/product')->load($id);
        $buy = Mage::helper('checkout/cart')->getAddUrl($_product);
        echo $qty = (int) Mage::getModel('cataloginventory/stock_item')->loadByProduct($_product)->getQty();

        //echo $id;
        //echo $this->getRequest()->getParam('id');;
    }
}
?>

    ----------------Change Add to cart code-------------------

    <?php if ($_product->isAvailable()): ?>
              <b class="available_quanity" style="display: none">Available Quantity :</b> <span id="simplestock" class="simplestock">Please select a color to view the quantity</span>
            <?php endif; ?>
            </div>
            <?php if(!$_product->isGrouped()): ?>
            <div class="qty">
                <label for="qty"><?php echo $this->__('Qty:') ?></label>
                  <?php $i = 0; ?>
                  <select id="qty" class="input-text" name="qty" style="width:50px;">
                    <?php while($i<=(int) Mage::getModel('cataloginventory/stock_item')->loadByProduct($_product)->getQty()):?>
                      <option value="<?php echo $i; ?>"><?php echo $i++; ?></option>
                    <?php endwhile; ?>
                  </select>
            </div>
            <?php endif; ?>

    ----------------Add Ajax for get Quantity---------------

    <script>
    jQuery(document).ready(function() {
        jQuery(".product-options select[id^='attribute']").on('change', function() {
            var id = getSimpleProductId();
            var qty = "";
            jQuery('.available_quanity').show();
            jQuery("#fancybox-loading").show();
            jQuery.ajax({      
                type: "POST",
                data: 'pid=' + id,
                url:'https://www.thewirelesscircle.com/guys/index/genCart',
                success:function(response){ 
                    if (response) {
                        qty = response;
                        var x = document.getElementById("qty");
                        var i;
                        removeOptions(x);
                        for(i=1;i<=qty;i++) {
                            var option = document.createElement("option");
                            option.text = i;
                            option.value = i;
                            x.add(option);
                        }
                    }
                    jQuery("#fancybox-loading").hide();
                }
            });

        });
    });

    </script>

    ---------------Get Selected Option Id in Magento-------------------

    <script type="text/javascript">
        function removeOptions(selectbox)
        {
            var i;
            for(i = selectbox.options.length - 1 ; i >= 0 ; i--)
            {
                selectbox.remove(i);
            }
        }
        function getSimpleProductId() {
            var productCandidates = [];
            jQuery.each(spConfig.settings, function (selectIndex, select) {
                var attributeId = select.id.replace('attribute', '');
                var selectedValue = select.options[select.selectedIndex].value;

                jQuery.each(spConfig.config.attributes[attributeId].options, function(optionIndex, option) {

                    if (option.id == selectedValue) {
                        var optionProducts = option.products;

                        if (productCandidates.length == 0) {
                            productCandidates = optionProducts;
                        } else {
                            var productIntersection = [];
                            jQuery.each(optionProducts, function (productIndex, productId) {
                                if (productCandidates.indexOf(productId) > -1) {
                                    productIntersection.push(productId);
                                }
                            });
                            productCandidates = productIntersection;
                        }
                    }
                });
            });
            return (productCandidates.length == 1) ? productCandidates[0] : null;
        }
    </script>

Answer 2

Donot need to load inventory module.

Just use isSaleable() of product model and it will work better.

<?php if ($product->isSaleable()):?>
<p class="availability in-stock"> <span class="label"><?php echo $this->helper('catalog')->__('Availability:') ?></span> <span class="value"><?php echo $this->helper('catalog')->__('In stock') ?></span> 
<span class="value">
<p>Delivery Time:</p>
<div id="delivery_time">
  <p>Delivery in 3 Days</p>
</div>
</span>
</p>
<?php } else: { ?>
<p class="availability out-of-stock"> <span class="label"><?php echo $this->helper('catalog')->__('Availability:') ?></span> <span class="value"><?php echo $this->helper('catalog')->__('Out of stock') ?></span> 
<span class="value">
<p>Delivery Time:</p>
<div id="delivery_time">
  <p>Delivery in 8 Days.</p>
</div>
</span>
</p>
<?php } endif; ?>

Answer 3

You can get the IDs of child products of a configurable product by using:

$ids = Mage::getResourceSingleton('catalog/product_type_configurable')
        ->getChildrenIds($_product->getId());

From here you can load the stock item directly (as you are using 1.9):

$stockItem = Mage::getModel('cataloginventory/stock_item')
           ->loadByProduct($ids[0]);

You may want to consider the efficiency of this and the fact that such information will be only available on the back-end. It might be better to extend getJsonConfig() in Mage_Catalog_Block_Product_View_Type_Configurable to add stock data. getJsonConfig() provides the config information available to javascript when manipulating the configurable options.

Answer 4

In my case configurables are always in stock, so I needed a way to get stock counts from the parent. Here's my implementation in 1.9.3.7

// Children Stock QTY
function getChildrenStockQTY($product, $stock_qty = 0) {
    if ($product->getTypeId() != 'configurable') return false;
    $simple_ids = Mage::getResourceSingleton('catalog/product_type_configurable')->getChildrenIds($product->getId());
    foreach ($simple_ids[0] as $simple_id) {
        $simple_model = Mage::getModel('cataloginventory/stock_item')->loadByProduct($simple_id);
        $stock_qty += $simple_model->getQty();
    }
    return $stock_qty;
}