Reflection in Elixir

Questions & Help Questions
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There are some tools and techniques that allow to do things comparable to what Java/.NET reflection APIs provide.

  • for inspecting current loaded/running BEAM applications use functions from elixir Application module (e.g. Application.all_started/0)
  • for working with loaded/complied module use erlang :code, e.g. `:code.all_loaded/0’
  • to fetch all functions/macros/callbacks of a given module use builtin functions __info__/1, module_info/0,1, `behaviour_info/1
  • Protocols provide some info by means of __protocol__/1, impl_for/1, impl_for!/1 functions
  • Struct can be converted to map with Map.from_struct/1 - use that to inspect/iterate over fields
  • Map can be converted to struct by putting special key e.g. Map.put(my_map, :__struct__, MyModule)
  • It is possible to generate code and compile modules on the fly (look into Code)
  • module alias is just an atom, you can generate it in the runtime by format string expressions, e.g. :"Elixir.My.#{prefix}Module"
  • you can invoke any function with apply
  • use Code.fetch_docs to query documentation
  • use Code.Typespec.fetch_specs/callbacks/types to query dialyzer specs (warning - private API)
  • use macros and Macro.pre/postwalk to generate/transform AST