Finding Your Way: Understanding Magento Code

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Finding Your Way
Understanding Magento Code // @benmarks
https://joind.in/talk/view/8147

Ben Marks
4.5 years doing Magento dev
2 years as a Magento U instructor
Happily employed at Blue Acorn in
Charleston, SC (we're hiring!)
Big fan of questions (ask away)
Who am I?

Who knows Magento?
Who are you?

Who hates Magento?
Who are you?

Who doesn't know Magento, but has been
told that they should hate it?
Who are you?

Who doesn't know Magento, but has been
told that they should hate it?
"Magento doesn't do anything very well" –
Harper Reed, php|tek, 2013
Who are you?

ZF1-based MVC framework
eCommerce Application
Answer to osCommerce
What is Magento?

LOTS of business
LOTS of developer community members
LOTS of room for innovation
LOTS of flexibility
Layout XML
What makes Magento awesome?

LOTS of undocumented features &
conventions
LOTS of bad information out there
LOTS of architecture to scale
LOTS of flexibility
Layout XML
What makes Magento difficult?

Supressed error output (index.php):
Caching on by default (Admin Panel):
Disabled output (admin), disabled local code
pool (app/etc/local.xml)
Getting Started: Don't Forget!

Declaration: app/etc/modules/
Code pool*
Type-specific folders
Theme assets
Modules & Module Structure

Declaration: app/etc/modules/
Points to app/code/core/Mage/Connect/etc/config.xml
All modules have config, and all config is merged
Modules & Module Structure

 Typical classname-to-path mapping, e.g.:
 See app/Mage.php & lib/Varien/Autoload.php:
app/code/local/, app/code/community/, app/cod
e/core/, lib/
 But... Magento is "all about options," so...
Typical Autoloading
Mage_Catalog_Model_Product_Type
Mage/Catalog/Model/Product/Type.php

 Reading class group notation
Mage::getModel('catalog/product_type')
<config>
<global>
<models>
<catalog>
<class>Mage_Catalog_Model
Factory Methods & Class Groups

 Allows for rewrites:
Mage::getModel('catalog/product_type')
<config>
<global>
<models>
<catalog>
<rewrite>
<product_type>New_Class

 Mage::getModel()
 Mage::helper()*
 Mage::app()->getLayout()->createBlock()
See Mage_Core_Model_Config
::getGroupedClassName()
That's the M, V, and H... but C works
differently

Standard route matching:
http://tek13.dev/catalog/product/view/id/51
frontName / controller / action
SEF rewrites: core_url_rewrite table
Controllers

Similar cofiguration-based approach, e.g.:
Mage/Catalog/etc/config.xml
Maps to Mage/Catalog/controllers/
Note: not autoloaded
Controllers

Class rewrite/additional route configuration:
Maps to Custom/Module/controllers/
Controllers

Mage_Core_Model_Layout
Factory method for instantiating blocks
Global block registry
Effectively a singleton, accessed via:
 $controller->getLayout()
 Mage::app()->getLayout()
 $block->getLayout()
The View: Layout Object

Blocks have two main workflows
 Instantiation: _construct() & _prepareLayout()
 Rendering:
toHtml(), _beforeToHtml(), _afterToHtml()
Blocks are generally responsible for
instantiating data models/collections –
important for view flexibility
The View: Blocks

Rendering is a waterfall down parent-child
relationships:
$parentBlock->getChildHtml('child');
$child->getChildHtml('etc');
//and so forth...
The View: Blocks

How do blocks get called in to scope for
rendering? In other words, how does stuff get
rendered?
The View: Blocks

Layout XML - up to the developer to use, not
use, mix as needed; keep controllers thin!
The View: Layout XML

Layout XML - up to the developer to use, not
use, mix as needed; keep controllers thin!
public function exampleAction()
{
$this->loadLayout()->renderLayout();
//$this->getResponse()->setBody('Hi!');
}

Declared in module config.xml; all module
layout XML files are compiled always
Layout Update Handles are responsible for
limiting the directives for current scope
Full Action Name handle – the missing link

<contacts_index_index />
<block /> - type, name, as, template
<reference /> - name
<remove /> - name
<update /> - handle
<action /> - method
action allows to call block public methods

Layout update handles: applied via PHP;
top-level nodes in layout XML files
Block type is class group notation:
<block type="page/html_head">
<action method="addJs">
<file>example.js</file>
Mage_Page_Block_Html_Head->addJs('example.js');

Parent-child relationships are established via
markup in layout XML...

...and this relationship is seen in templates as
well:
Required for rendering to work

Parent-child block relationships can also be
set/unset using <action />:
<reference name="root">
<action method="unsetChild">
<child>content</child>
</action>
</reference>
Child exists, but "outside" of rendering flow

Most important thing to understand:
Via layout XML any module can affect any view
through the full action name handle or other
applied handle (customer_logged_in, etc.)
Let's see some examples from catalog.xml

Config XML is composed of the following:
 app/etc/*.xml
 app/etc/modules/*.xml
 All active module config.xml
 app/etc/local.xml
 core_config_data table
Configuration XML

Confusingly accessed/evaluated/built; better
to learn it by application
Important top level nodes:
 global
 frontend & adminhtml
 admin
 default, websites, & stores; often, user-
configurable values here
Configuration XML

Website and store scopes are admin-
configurable, but affect config DOM
structure (System > Manage Stores)
Possible to declare same xpaths in multiple
files and in core_config_data table* (*for
default, websites, and stores)
Colliding xpath text values are overwritten
when merged
Configuration XML

Convenience method for reading correct
value for store scopes
Mage::getStoreConfig('foo/bar/baz');
//same as...
Mage::getConfig()->getNode(
'stores/[code]/foo/bar/baz'
);
Configuration XML

Sometimes it's the node name being
evaluated (e.g. module declaration); most of
the time it's the text node
Bottom line, it's all about the xpath and the
PHP which is evaluating it
Configuration XML

System XML is the quickest way to add user-
configurable fields to the admin panel
Default values can be set in files or added to
core_config_data via setup scripts
Let's look at Mage/Contacts/etc/system.xml
System XML

Magento CRUD:
 Create & Update: save()
 Read: load()
 Delete: delete()
Data model CRUD works through resource
model (see Mage_Core_Model_Abstract)
The Model Layer: CRUD

Hybrid resource / data model classes
Filtering, sorting, etc. Lazy loaded.
Implement Countable &
IteratorAggregate, making it possible to do
this:
The Model Layer: Collections

Generally the best way to customize
Events are dispatched throughout core code
Allow to execute code uniformly (e.g. during
request dispatching) or during specific flow
of execution (catalog_product_load_after)
Observers

Varien_Object (lib/Varien/Object.php)
Basis of blocks and models; for
models, methods map to table columns or
attributes
get*, set*, uns*, & has*
$model->getFooBar()
reads from
$model->_data['foo_bar']
Missing code: when __call strikes

Caveat: nothing stops classes from defining
getters, setters, etc.
Don't var_dump() objects directly; use
Varien_Object->debug() to see
properties in _data
Missing code: when __call
strikes

The action and the template are the most
important aspects to deciphering layout
XML; not all blocks use template!
Find the block class via type
Check the definition to see if the method is
declared or not
A simple echo get_class($this) in the
template will suffice
Missing code: layout XML

Observer configuration can be found mainly
under the xpaths
global/events, frontend/events, and
adminhtml/events
Many events are dynamic
Multiple observers can be configured for the
same event
Missing code: Observers

When an install is not behaving as
expected, check for Mage, Varien, and Zend
namespaces outside of core or lib
Check for event observer configuration for
targeted CRUD and reques operations
Missing code: Miscellaneous

When content is being rendered with no
apparent source in template or entity
data, suspect translations, which can reside
in translate.csv, app/locale/, or core_translate
table; translate="" & __("Some String")
CMS pages, categories, and products all
have custom design settings (themes &
layout XML) which are stored in the
database
Missing code: Miscellaneous

Module code not executing.
Is config being merged? Enable developer
mode & clear cache. Error message indicates
everything is ok. 80% of all problems start
with config.*
Troubleshooting Process

Unexpected or missing theme-related content.
Reset the theme to default to rule out issues
from custom templates & layout XML; check
database for layout XML, template, and theme
settings. Check parent-child relationships.

Class XYZ is not behaving correctly.
Check for a config-based rewrite, an include
path override, or an event observer.
Collection class/view seems to be slow.
Ensure that the collection class is building
correct data and that models are not being
loaded iteratively.

Enable profiler in two places:
 System > Configuration > Developer
 index.php - uncomment Varien_Profiler::enable()
Rudimentary output; read from outside-in till
you get to the bottom-most entry with longest
execution time
Enable query profiler in config xml at
global/resources/default_setup/connection/profiler
Profiler

 Enable TPH in admin:
 System > Configuraration > Developer
 Change scope from "Default"
 Pretty ugly, and missing key info (such as
alias, name). Check out AOE_TemplateHints
v2.0 http://www.fabrizio-branca.de/magento-
advanced-template-hints-20.html
Template Path Hints

ben@blueacorn.com
http://twitter.com/benmarks
Me

http://stackoverflow.com/questions/tagged/
magento
http://magento.stackexchange.com/
http://alanstorm.com/
http://magebase.com/
http://www.fabrizio-branca.de/magento-
modules.html
http://blueacorn.com/
Resources

Magicento plugin for PhpStorm
http://magicento.com/
n98-magerun:
https://github.com/netz98/n98-magerun
Feedback:
https://joind.in/talk/view/8147
Resources

Finding Your Way: Understanding Magento Code

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