Redirect Magento to checkout onepage after adding item to cart

Question

How can I redirect the user after it adds one item to the cart?
lets say I want him to choose one item and go to the checkout/onepage, how can I do that?

Answer 1

Using checkout_cart_add_product_complete you will miss out on product addtocart success message check this

Mage::dispatchEvent('checkout_cart_add_product_complete',
                    array('product' => $product, 'request' => $this->getRequest(), 'response' => $this->getResponse())
                );

if (!$this->_getSession()->getNoCartRedirect(true)) {
 if (!$cart->getQuote()->getHasError()) {
         $message = $this->__('%s was added to your shopping cart.', Mage::helper('core')->escapeHtml($product->getName()));
               $this->_getSession()->addSuccess($message);
     }
       $this->_goBack();
}

Again if you don't wont the session messages, just pass additional parameter from your product page

No need for any other customization or module creation, its magento's default functionality