developer-delphi-programming-conditional-defines

Delphi conditional defines let you toggle database engines by checking directives in a specific order: UNIDAC, FIREDAC, ZEOS, then SQLDB. You place these {$IF DEFINED(...)} blocks in an ORM.Defines.inc file to safely enable or disable engines at compile time across projects.

The correct order for checking conditional compilation directives is UNIDAC, FIREDAC, ZEOS, then SQLDB. Following this canonical sequence in your {$IF DEFINED(...)} blocks ensures safe fallbacks and consistent engine activation across both Delphi and Free Pascal compilers.

Yes, you can use a canonical ORM.Defines.inc file for cross-compiler builds between Delphi and FPC. This approach provides a safe, shared pattern for {$IF DEFINED(...)} blocks, ensuring consistent feature toggling and engine activation across both compilers.

You enable optional modules like USE_ENTITY_MANAGER and USE_QUERY_BUILDER by declaring them as conditional defines within your ORM.Defines.inc file. This compile-time directive approach also applies to USE_ATTRIBUTES, USE_PARAMENTERS, USE_LOGGERS, and USE_POOLCONNECTIONS.

The best way to organize conditional compilation blocks is by consolidating them into a canonical ORM.Defines.inc file. This enforces the dictated engine check order and safe nesting patterns for {$IF DEFINED(...)} blocks, ensuring reliable multi-target builds.

Conditional compilation directives fail to switch engines correctly when the canonical check order is ignored. You must verify that your {$IF DEFINED(...)} blocks follow the UNIDAC to SQLDB sequence and include proper fallbacks within your ORM.Defines.inc file.