A Beginner's guide to Complex Data Types

An introduction on how to spot composite types hiding in your code and ways to model and persist them.

Transcript

1. A BEGINNER’S GUIDE TO: COMPLEX DATA TYPES
2. DENIS BRUMANN denis.brumann@sensiolabs.de @dbrumann
3. What am I talking about? Latitude and longitude
 form a unit If one is missing or invalid the coordinates are invalid
4. Definition In computer science, a composite data type or compound data type is any data type which can be constructed in a program using the programming language's primitive data types and other composite types. — https://en.wikipedia.org/wiki/Composite_data_type
5. Typical cases Money Coordinates Address Recurring cycles involving e.g. a combined year + month, like 2017/02, form a term (e.g. for reports) An entity’s ID combined with another property
 (e.g. a revision number or date) forming composite ID
6. Money https://github.com/moneyphp/money
7. GeoPHP https://geophp.net/ https://github.com/phayes/geoPHP
8. How to spot complex types? Long list of properties or large number of constructor arguments
9. How to spot complex types? Mismatch between database and code can be an indicator; having to combine primitive types before fetch/insert
10. How to spot complex types? Splitting or combining data in getters/setters
11. How to spot complex types? Special/recurring rules for outputting
12. How to spot complex types? Conditionals involving multiple primitive types Bonus points for when (InvalidArgument)Exceptions are involved
13. What not to do with them? Don’t incorporate them in other entities* Don’t duplicate the logic in your code Don’t spread the logic * it depends
 — Don’t rip apart your entities just for the sake of having smaller, coherent types
14. If you have to keep mutability Sanity checks avoid inconsistent state External validation is an option
15. PHP 7 is your friend Return types will cause a (catchable) TypeError to be thrown when value was not set before
16. If you have to keep mutability Should a model decide
 it’s own validity?
17. Immutability Immutability helps with consistency Keep logic inside the object Check constraints during construction
18. Complex made from complex Keeps things simple Avoid chained calls
19. Factory methods Factory methods provide convenience and help expressing edge case
20. Keep alternations together alternate formats in one place makes changes easier
21. Database mapping Advanced field value conversion using custom mapping types http://docs.doctrine-project.org/ projects/doctrine-orm/en/latest/ cookbook/advanced-field-value- Separating concerns using Embeddables http://docs.doctrine-project.org/ projects/doctrine-orm/en/latest/ tutorials/embeddables.html
22. Persisting complex types Custom Doctrine Mapping type
23. Mapping Type converts back and forth between database field and property
24. Embeddables Declare complex type as Embeddable and map properties to database fields Use @Embedded in your Entity
25. Thanks