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Introduction to DDD
Adam Štipák | @new_POPE | rekurzia.sk
Who I am?
Adam Štipák@new_POPE
rekurzia.sk
● since 2006
● Sven Creative
● Sygic
● Diagnose.me
● and other “secret” projects
What is DDD?
“is an approach to software development for complex needs by connecting the implementation to an evolving model”
- wikipedia.org
● Useful and meaningful model of its Domain
● Domain Experts contribute to software design
● Better user experience
● Clear boundaries
● Better architecture organization
● Iterative and continuous modeling in an Agile fashion
● better tools, both strategic and tactical design
Why DDD?
Architectural styles - old layered architecture
Architectural styles - MVC
Architectural styles - Hexagonal architecture
The dependecy inversion principle
“High-level modules should not depend on low-level modules. Both should depend on abstractions.
Abstractions should not depend on details. Details should depend on abstractions.”
- Robert C. Martin
Ubiquitous language
“When we recieve a new order, system sends a
notification”
Ubiquitous language
What is the new order?
Bounded context
Building blocks
Value Objects
● Immutable
● “comparable”
Entities
● Identifiable
● Consistent
● Avoid ANEMIC MODEL
○ setSong(newSong)
○ replaceSong(newSong)
Aggregates
● lists, maps, etc
● order, clinic visit, playlist
is a cluster of domain objects that can be treated as a single unit.
… says Martin Fowler
Factories
● creates something
● create(...)
Repositories
● Collection oriented
○ get(ID), add(), addAll(), remove()
● Persistent oriented
○ get(ID), save(), saveAll(), ...
Services
● stateless
● singleton (not Singleton pattern)
○ e.g. ne instance in DI container
● SRP!
Domain Events
● contains data
● immutable
E.g.
● born
● song replaced
● song on cassette was cleared
Resources
● The blue book● The red book
● Domain Driven Design Quickly● Domain-Driven Design in PHP
???Questions ???Adam Štipák | @new_POPE | rekurzia.sk
Thank you!Adam Štipák | @new_POPE | rekurzia.sk
