Best Practices in Magento 2 Development using MSI project as an example by Valeriy Nayda at Khmelnytskyi Magento Meetup.

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Best practices in
Magento 2
Based on Multi-Source Inventory (MSI)
project

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Valeriy Naida
Magento Developer, Multi Source Inventory
Community Engineering Team

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In one of our directions we have started to work with Community
• Benefit for Magento is creation of new important feature
• Benefit for Community is an increase in knowledge about Magento 2
• Provide a set of best practices how to work with Magento 2 (some
cookbook)
Community Engineering Team

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• What is API / SPI in Magento 2 (more practice)
• Repository responsibility in Magento 2
• Use Composition instead of Inheritance / Traits
• Object Manager should not be used as a class dependency
…
• There is no silver bullet (Think first!)
Frequently asked questions

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API / SPI concepts in
Magento 2

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API - Interfaces for usage (calling) in the client
code
Located in Api subfolder or in the separate module
ApiModule
API

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SPI - Interfaces that you should extend and
implement to customize current behavior
But NOT expected to be used (called) in the client
code directly
Located near implementation
SPI

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Q: Can the API and SPI be a single interface?
A: Yes. It often happens. Do not create empty proxy (API to SPI) classes
FAQ

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Q: Can I call one API from another?
A: Yes. You could create Sugar Service to avoid boilerplate code
=>
• But provide clear DocBlock
• Try to keep a single point of Customization
FAQ

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Q: What about Resource Model?
A: TBD
Q: When is needed to add SPI?
A: TBD
Q: Why not introduce the @spi annotation?
A: TBD
FAQ

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1. Main logic is API
2. Steps (strategies) are SPI
Algorithm example

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Repository responsibility
In Magento 2

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In Magento 2 Repository is considered as an implementation of Facade
pattern which provides a simplified interface to a larger body of code
responsible for Domain Entity base management
BUT Repository is NOT new kind of “helper”
Facade pattern

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Repository under hood
Usually typical repository provides the following methods:
Could NOT be wider than methods mentioned above

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Repository under hood
List of the methods could be shorter if based on the business requirements
particular entity doesn't have some of the operation(-s)

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Repository under hood
Methods with their own semantic recommended to be put into some dedicated
Services
• Principle Of Least Surprise
• Backward compatibility

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DDD liked services instead of Repository
Link between Source and Stock doesn’t have sense from business side

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Repository Implementation

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1. Repository could be considered as an API - Interface for usage (calling) in
the business logic
2. Separate class-commands to which Repository proxies initial call (like, Get
Save GetList Delete) could be considered as SPI
Repository: API vs SPI segregation

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Object Manager should
not be used as a class
dependency

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Generally Object Manager should not be used as a class dependency
Problems:
• Class is hard coded and can not be replaced with a different one
• Would require more work to modify the behavior by third parties
Object Manager

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There is no good possibility to replace Logger object only for this Class
Example - Problem

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Example - Solution

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Object Manager could be used in classes which create objects
(Factories, Builders, Pools)
When Object Manager is applicable

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May also be used to maintain Backwards Compatibility
When Object Manager is applicable

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Composition against
Inheritance

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Inheritance / trait should not be used. Composition should be used
instead
Problems:
• Inheritance enforces dependency on a specific parent class which can not be
replaced in runtime
• Would require more work to modify the behavior by third parties
Inheritance

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Requires complete replacement of the
renderer, instead of customizing it
Example - Problem

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• Price Formatter may be easily
replaced by injecting another
dependency in the constructor
• Allows precise modification of
behavior
Example - Solution

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• Class is a Subtype of another class
• Template Method pattern (usually with Hollywood Principle: Don't call us,
we'll call you)
• You don’t need replaceability
When Inheritance / trait is applicable

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Provides possibility of saving entity with predefined/pre-generated id (quick
solution in waiting for the ORM)
IS NOT supposed to be replaced

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Useful Links

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• Magento 2 Technical Guidelines
http://devdocs.magento.com/guides/v2.2/coding-standards/technical-
guidelines/technical-guidelines.html
• Backward compatible development
http://devdocs.magento.com/guides/v2.2/contributor-guide/backward-
compatible-development/
• Multi-Source Inventory (MSI) project
https://github.com/magento-engcom/msi/wiki
Useful Links

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Exchange Ideas

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How to join us? Send an email to
engcom@magento.com
@_naydav
Thank y’all!