Full mruby interpreter with simple bindings, allowing for easy scripting support in projects mruby scripting ruby
1.1.0 Latest release released
149 7 2


Anyolite is a Crystal shard which adds a fully functional mruby (or even regular Ruby) interpreter to Crystal.


Release ReleaseDate



Anyolite allows for wrapping Crystal classes and functions into Ruby with little effort. This way, Ruby can be used as a scripting language to Crystal projects, with the major advantage of a similar syntax.

Useful links for an overview:

  • Demo project:
  • Wiki:
  • Documentation:


  • Bindings to an mruby interpreter
  • Near complete support to regular Ruby as alternative implementation (also known as MRI or CRuby)
  • Wrapping of nearly arbitrary Crystal classes and methods to Ruby
  • Easy syntax without unnecessary boilerplate code
  • Simple system to prevent garbage collector conflicts
  • Support for keyword arguments and default values
  • Objects, arrays, hashes, structs, enums and unions as function arguments and return values are completely valid
  • Ruby methods can be called at runtime as long as all their possible return value types are known
  • Ruby closures can be handled as regular variables
  • Methods and constants can be excluded, modified or renamed with annotations
  • Options to compile scripts directly into the executable


You need to have the following programs installed (and in your PATH variable, if you are on Windows):

  • Ruby (for building mruby)
  • Rake (for building the whole project)
  • Git (for downloading mruby)
  • GCC or Microsoft Visual Studio 19 (for building the object files required for Anyolite, depending on your OS)

Using regular Ruby instead of mruby

It is possible to use Anyolite with regular Ruby (MRI) instead of mruby. An instruction to install MRI can be found at Using Ruby instead of mruby in the wiki.


Put this shard as a requirement into your shard.yml project file and then call

shards install

from a terminal.

Alternatively, you can clone this repository into the lib folder of your project and run

rake build_shard

manually from a terminal or the MSVC Developer Console (on Windows) to install the shard without using the crystal shards program.

If you want to use other options for Anyolite, visit Changing build configurations in the wiki.

How to use

Imagine a Crystal class for a really bad RPG:

module RPGTest
  class Entity
    property hp : Int32

    def initialize(@hp : Int32)

    def damage(diff : Int32)
      @hp -= diff

    def yell(sound : String, loud : Bool = false)
      if loud
        puts "Entity yelled: #{sound.upcase}"
        puts "Entity yelled: #{sound}"

    def absorb_hp_from(other : Entity)
      @hp += other.hp
      other.hp = 0

Now, you want to wrap this class in Ruby. All you need to do is to execute the following code in Crystal (current commit; see documentation page for the version of the latest release):

require "anyolite"

Anyolite::RbInterpreter.create do |rb|
  Anyolite.wrap(rb, RPGTest)


Well, that's it already. The last line in the block calls the following example script:

a = 20)
a.damage(diff: 13)
puts a.hp

b = 10)
a.absorb_hp_from(other: b)
puts a.hp
puts b.hp
b.yell(sound: 'Ouch, you stole my HP!', loud: true)
a.yell(sound: 'Well, take better care of your public attributes!')

The example above gives a good overview over the things you can already do with Anyolite. More features will be added in the future.


See Limitations and solutions in the Wiki section for a detailed list.

Why this name?

In short, it is a rare variant of the crystalline mineral called zoisite, with ruby and other crystal shards (of pargasite) embedded.

The term 'anyoli' means 'green' in the Maasai language, thus naming 'anyolite'.


Upcoming releases

None yet

Later releases

  • [ ] Automated generation of Ruby documentations for wrapped functions
  • [ ] MRI support on Windows (does currently not work for some reason)
  • [ ] MRI support for version 3.1.0 and up
  • [ ] Support and continuous integration for Mac
  • [ ] Support for bindings using Data and Struct from Ruby
  • [ ] Multiple interpreters for mruby
  • [ ] Add option to make script calls thread-safe

Wishlist, entries might not be possible to implement

  • [ ] Splat argument and/or arbitrary keyword passing
  • [ ] Support for slices and bytes
  • [ ] Classes as argument type
  • [ ] Resolve context even in generic type union arguments
  • [ ] General improvement of type resolution
  • [ ] Bignum support
  • [ ] Range support
  github: Anyolite/anyolite
  version: ~> 1.1.0
License MIT
Crystal >= 1.0.0


  • Hadeweka

Dependencies 0

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