WC_Data, Data Storage & Manipulation
Overview
A few key concepts are at the base of all WC_Data objects. Understanding how the class getsIn “getter” methods, manipulatesWith “setter” methods and stores dataWith “update” methods can provide insights into how you can set various classes to interact with custom data involved in your project. In this section we’ll look at:
- The concepts of data, extra_data, and meta_data
- WC_Data’s methods
WC_Data Properties
data vs extra_data
WC_Order_Item $data
WC_Order_Item $extra_data
The $data property is used to hold information that is fundamental to the representation of the class family. The $extra_data propertyPrimarily used by the product, order_item, and payment token families is used by descendants of the family to add data without overwriting the $data settings.
data vs extra_data vs meta_data
- While data is the core information, and extra data is the inheritance information, meta_data is the location for storing completely non-standard, custom information.
- In most cases, the specific table utilized for storing metadata is defined by the data store’s $meta_type property. This is a feature implemented by the WC_Data_Store_WP class
- $meta_data utilizes the WC_Meta_Data class to monitor changes to this property, in order to minimize unnecessary database writes.
The WC_Meta_Data class helps ensure that WC_Data’s save_meta_data() method does not perform any unnecessary database writes.
WC_Data methods
| __construct | __sleep | __wakeup | __clone | get_data_store |
| delete | save | __toString | get_data | get_data_keys |
| filter_null_meta* | get_meta_data | is_internal_meta_key* | get_meta | meta_exists |
| add_meta_data | update_meta_data | delete_meta_data | delete_meta_data_by_mid | maybe_read_meta_data* |
| save_meta_data | set_id | set_defaults | set_object_read | get_object_read |
| set_prop* | get_changes | apply_changes | get_hook_prefix | get_prop* |
| error* | get_id | set_date_prop* | set_props | read_meta_data |
| read_meta_data | set_meta_data | get_extra_data_keys |
* method is protected (only available when writing methods within descendants of WC_Data)
Special methods
-
__construct( integer|object|array $read = 0 )
A data object can be created from a database read, or by receiving defining properties, or with no properties (it will be assigned default properties) -
__sleep()
PHP magic method, Ensure only the data object’s id is serialized -
__wakeup()
PHP magic method, Constructs the object from the id in the serialized array -
__clone()
PHP magic method, Used to ensure that the meta data is cloned properly by cloning the instances of WC_Meta_Data -
__toString()
PHP magic method, Uses wp_json_encode() to control string conversions -
error( $code, $message, $http_status_code = 400, $data = array() )
Throws a WC_Data_Exception, specific to invalid data in a WC_Data object
Database operation methods
- delete()
- save()
- read_meta_data( $force_read = false )
- save_meta_data()
- maybe_read_meta_data() WooCommerce uses this to prevent unnecessary database reads. $data->read_meta_data(true) will force fresh reads.
Getters
- get_data_store()
- get_id()
- get_data()
- get_data_keys()
- get_extra_data_keys()
- get_meta_data()
- get_meta( $key = ”, $single = true, $context = ‘view’ )
- get_object_read()
- get_changes()
- get_hook_prefix()Used to determine an object’s hooks/filters
- get_prop( $prop, $context = ‘view’ )This is the core method for most getters
- set_date_prop( $prop, $value )
Setters
- set_meta_data( $data )
- add_meta_data( $key, $value, $unique = false )
- update_meta_data( $key, $value, $meta_id = 0 )
- delete_meta_data( $key )
- delete_meta_data_by_mid( $mid )
- delete_meta_data( $key )
- delete_meta_data_by_mid( $mid )
- set_defaults()
- set_object_read( $read = true )
- set_props( $props, $context = ‘set’ )Used by data stores to load class
- set_prop( $prop, $value )Core method for most setters
- apply_changes()Does NOT automatically result in a database write
Checkers (Boolean)
- filter_null_meta( $meta )
- is_internal_meta_key ( $key )
- meta_exists( $key = ” )
Conclusion
Now that you understand the difference between the different data types, and understand the methods at the core of WC_Data functionality, you can start to see the opportunities for easy customization.
In the next topic, we’ll look at how Data Stores are used provide a flexible method of database storage for WC_Data objects
But first, check your knowledge.
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