Data Stores
Overview
Data Stores provide a layer of abstraction between the working WC_Data object and the information stored in the database. In understanding how they work, you’ll know what your objects are doing when they create, load, save, and delete; and how to customize these behaviors. In this topic, we’ll cover:
Interfaces
- The WC_Object_Data_Store_Interface defines the methods required for a WC_Data object
- Each family of WC_Data (e.g. product, coupon, order-item, etc.) has it’s own interface to identify specific methods for that family’s data stores to operate reliably
- When implementing a custom data store, both WC_Object_Data_Store_Interface and the family-specific interface should be implemented.
- However, the WC_Data_Store class will only verify that the loaded datastores implement WC_Order_Data_Store_Interface. The constructor method of the WC_Data_Store class does an instanceof check (on line 94) Failure to use the family ‘assistant’ interfaces will not automatically throw an Error
Assistant Interfaces
- WC_Customer_Data_Store_Interface
- WC_Customer_Download_Data_Store_Interface
- WC_Customer_Download_Log_Data_Store_Interface
- WC_Object_Data_Store_Interface
- WC_Order_Data_Store_Interface
- WC_Order_Item_Data_Store_Interface
- WC_Order_Item_Product_Data_Store_Interface
- WC_Order_Item_Type_Data_Store_Interface
- WC_Order_Refund_Data_Store_Interface
- WC_Payment_Token_Data_Store_Interface
- WC_Product_Data_Store_Interface
- WC_Product_Variable_Data_Store_Interface
- WC_Shipping_Zone_Data_Store_Interface
- WC_Webhook_Data_Store_Interface
Interface Methods
- Notice that each method in the interface receives the Data Object $data, which is passed by reference. In implementation this is an instantiated object, such as a product, or order item
- Consequently each $data_store directly edits it’s $data object with database information
- This is primarily used so that the data store can easily set_props in the WC_Data object as it interacts with the database
Data Store methods
| WC_Data object method | Data Store method |
|---|---|
| __construct($id | $object) | read($data) |
| save() | create($data) update($data) |
| delete($force_delete) | delete($data, $args) |
| read_meta_data() | read_meta($data) |
| save_meta_data() |
delete_meta($data, $meta) add_meta($data, $meta) update_meta($data,$meta) The data_store uses WC_Meta_Data to assess which methods are necessary and minimize database transactions |
WC_Data_Store_WP: The Fundamental Default Data Store Class
- WC_Data_Store_WP is a foundational class but it’s use is not requiredThe generic parent class for a CPT data object’s data store
- The WC_Data_Store_WP class does NOT fully implement the WC_Object_Data_Store_Interface Meaning, you must add the interface methods after you extend it.
- It provides methods for using WordPress’s custom post types, metadata, taxonomy, WP_Query, and Search APIs
- Descendants of WC_Data_Store_WP override this functionality as necessary (e.g. the Abstract_WC_Order_Item_Type_Data_Store)
WC_Data_Store_WP Properties
Properties held in WC_Data_Store_WP. Developers implementing custom data stores that descend from
WC_Data_Store_WP should set these property values as necessary.Note: one of the chief complaints against WooCommerce
is that it stores too much data in the postmeta table. This is where you can implement solutions
WC_Data_Store_WP lookup tables
- Lookup tables provide a mechanism for improving read and write efficiency over typical meta tables
- The WC_Product_Data_Store provides an example of this in the wc_product_meta_lookup table
- Key methods supporting this feature are:
- get_data_for_lookup_table( $id, $table) Note: this returns an empty array in the foundational class
- get_primary_key_for_lookup_table($table) Note: this returns an empty string in the foundational class
- update_lookup_table($id, $table) By implementing the above two methods, the update and delete methods will function
- delete_from_lookup_table($id, $table)
Structure of the wc_product_meta_lookup table.
Conclusion
Now that you know the interfaces that define data stores, and how the data store methods map to the WC_Data methods, you should feel more confident in your ability to navigate transactions between WC_Data object and the database. These two concepts are the keys to creating your own data stores, and fully customizing a WC_Object’s behavior.
Next, we’ll take a quick tour of each of the WC_Data families.
But first, check your knowledge.
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