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reflection

README.md

C++ Static Reflection library for Thrift

This is the C++ static reflection library for Thrift, which provides reflection support at compile-time through the use of meta-programming.

Usage

Since there's no native support for static reflection in C++, Thrift will generate some metadata to ensure portability. This metadata needs to be included to enable static reflection support.

Static reflection is only provided for the cpp2 language backend, but it's backwards compatible with cpp through the existing compatibility option from cpp2.

To direct Thrift to generate the static reflection metadata, use the reflection option for the cpp2 language:

$ thrift --gen cpp2:reflection MyModule.thrift

Thrift breaks the metadata up in different headers to help reduce compilation times, so that a user can include only what's needed. To include this metadata in your code, include the appropriate header containing the metadata you need, as described below.

Say your module is defined in some_dir/MyModule.thrift, these headers will be generated:

  • some_dir/gen-cpp2/MyModule_fatal.h: general module metadata. Necessary when using reflect_module and related primitives;
  • some_dir/gen-cpp2/MyModule_fatal_types.h: metadata for all types declared in the module, necessary when using reflect_struct, reflect_enum, fatal::enum_traits, reflect_variant, fatal::variant_traits and related primitives;
  • some_dir/gen-cpp2/MyModule_fatal_all.h: convenience header that includes all the static reflection metadata generated by the Thrift compiler.

Documentation

Most documentation can be found inline in the header files under the reflection library directory.

There are some demo applications unside the demo/ directory.

There's a video from the CppCon 2016 presentation that goes through the basics of reflection, as well as some of the demo applications. The accompanying slides with additional examples can be found in the docs/ directory.

Dependencies

Thrift's C++ Static Reflection makes use of the Facebook Template Library to abstract most of the template meta-programming.

Troubleshooting

The most common issue by far is forgetting to add some of the metadata headers generated by Thrift. Refer to the Usage section for more information.