ffi_sample.rb

require 'ffi'

module FFISample
  extend FFI::Library

  ffi_lib 'target/release/libffi_sample.dylib'

  class SampleStruct < FFI::Struct
    layout :i, :int,
           :b, :bool,
           :s, :string
  end

  attach_function :create_sample_struct, [:pointer], :void
end

st = FFISample::SampleStruct.new

FFISample.create_sample_struct(st.pointer)
puts "i: #{st[:i]}, b:#{st[:b]}, s:#{st[:s]}"