Reflection Compilation Levels

Three different compilation modes for reflection support with varying runtime capabilities.

The reflection system supports three compilation levels:

Full reflection: Complete metadata and runtime support for type registration and function calls
Metadata-only (VCZH_DESCRIPTABLEOBJECT_WITH_METADATA): Type metadata without runtime support
No reflection (VCZH_DEBUG_NO_REFLECTION): Reflection disabled entirely Always prefer code compatible with VCZH_DEBUG_NO_REFLECTION when possible.

Compilation Levels

Full Reflection (Default)

When no special macros are defined, VlppReflection compiles with full reflection support:

Complete metadata and runtime support for type registration and function calls
You can register your own classes, get metadata from registered types and objects, and call reflectable functions at runtime
Executing a Workflow script runs in this level
Use vl::reflection::description::GetTypeDescriptor<T> to get the metadata of a type

Metadata-Only Mode

Defined by VCZH_DESCRIPTABLEOBJECT_WITH_METADATA:

Metadata of types are loaded from external sources
You can get metadata from types, but lose all runtime support
Running a Workflow or GacUI XML compiler operates in this level
Type information is available but dynamic invocation is not supported

No Reflection Mode

Defined by VCZH_DEBUG_NO_REFLECTION:

Reflection is completely disabled
Workflow or GacUI XML Compiler generated code should be able to run in this level
Minimal runtime overhead
No metadata or dynamic capabilities available

Best Practices

Always prefer code that is compatible with VCZH_DEBUG_NO_REFLECTION when possible. This ensures:

Maximum performance with minimal overhead
Broader compatibility across different compilation scenarios
Cleaner separation between reflection-dependent and reflection-independent code

When reflection is enabled (when VCZH_DEBUG_NO_REFLECTION is not defined), you can access type metadata and perform dynamic operations.

Extra Content

Conditional Compilation Patterns

Use conditional compilation to handle different reflection levels:

#ifndef VCZH_DEBUG_NO_REFLECTION
    // Code that requires reflection
    auto typeDescriptor = vl::reflection::description::GetTypeDescriptor<MyClass>();
#endif

Performance Considerations

Full reflection: Highest capability, highest overhead
Metadata-only: Medium capability, medium overhead
No reflection: No reflection capability, minimal overhead

Choose the appropriate level based on your application's requirements for dynamic behavior versus performance.

2.6 KiB Raw Blame History