Powerful block system in Magento-优快云博客

When you read the class<wbr>Mage_Core_Block_Abstract,you will know that magento creates a very powerful block system. <div><br></div> <div>First of all,<wbr>Mage_Core_Block_Abstract is thesubclass of<wbr>Varien_Object. That is to say, magentospecific block class whose parent classis<wbr>Mage_Core_Block_Abstract can add as many childblocks as possible and access them in the array-style way.</wbr></wbr></wbr> </div> <div><br></div> <div><wbr><wbr> public functionsetChild($alias, $block)</wbr></wbr></div> <div> <div><code><wbr><wbr> {</wbr></wbr></code></div> <div><wbr><wbr><wbr><wbr> if (is_string($block)) {</wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr><wbr><wbr> $block =$this->getLayout()->getBlock($block);</wbr></wbr></wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr> }</wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr> if (!$block) {</wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr><wbr><wbr> return$this;</wbr></wbr></wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr> }</wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr>$block->setParentBlock($this);</wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr>$block->setBlockAlias($alias);</wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr> $this->_children[$alias] =$block;</wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr> return $this;</wbr></wbr></wbr></wbr></div> <div><wbr><wbr> }</wbr></wbr></div> </div> <div><br></div> <div>Moreover, Magento provides two ways to use block: XML layoutway and object way.</div> <div><br></div> <div>1.Use XML layout way</div> <div><br></div> <div> <div><catalog_category_default></div> <div><wbr><wbr><wbr><wbr> <referencename="left"></wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr><wbr><blocktype="directory/currency" name="currency"template="directory/currency.phtml"/></wbr></wbr></wbr></wbr></wbr></div> <div><wbr><wbr><wbr><wbr> </reference></wbr></wbr></wbr></wbr></div> <div></catalog_category_default></div> <div><br></div> </div> <div>In the template file, use following statement<?php echo$this->getChildHtml("currency");?></div> <div><br></div> <div>2.Object way</div> <div><br></div> <div><?php</div> <div>$currency =new<wbr>Mage_Directory_Block_Currency();</wbr> </div> <div>echo<wbr><span style="line-height:21px">$currency->toHtml();</span></wbr> </div> <div>?></div> <div><br></div> </wbr>