A BEGINNER’S GUIDE TO: COMPLEX DATA TYPES 

DENIS BRUMANN [email protected] @dbrumann 

What am I talking about? Latitude and longitude
 form a unit If one is missing or invalid the coordinates are invalid 

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 

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 

Money https://github.com/moneyphp/money 

GeoPHP https://geophp.net/ https://github.com/phayes/geoPHP 

How to spot complex types? Long list of properties or large number of constructor arguments 

How to spot complex types? Mismatch between database and code can be an indicator; having to combine primitive types before fetch/insert 

How to spot complex types? Splitting or combining data in getters/setters 

How to spot complex types? Special/recurring rules for outputting 

How to spot complex types? Conditionals involving multiple primitive types Bonus points for when (InvalidArgument)Exceptions are involved 

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 

If you have to keep mutability Sanity checks avoid inconsistent state External validation is an option 

PHP 7 is your friend Return types will cause a (catchable) TypeError to be thrown when value was not set before 

If you have to keep mutability Should a model decide
 it’s own validity? 

Immutability Immutability helps with consistency Keep logic inside the object Check constraints during construction 

Complex made from complex Keeps things simple Avoid chained calls 

Factory methods Factory methods provide convenience and help expressing edge case 

Keep alternations together alternate formats in one place makes changes easier 

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 

Persisting complex types Custom Doctrine Mapping type 

Mapping Type converts back and forth between database field and property 

Embeddables Declare complex type as Embeddable and map properties to database fields Use @Embedded in your Entity 

Thanks