Question

Is there a way that I can load a user-defined Ruby input file into my application in a way that I can access any variables, methods, and classes defined in the input file?. An example input file might look like this:

def my_callback(t)
    t ** 2
end
parameter_x = "10 bytes"
parameter_y = my_callback

In my application, I would like to do something like the following:

input = load_input_file
puts input.parameter_x     # => "10 bytes"
puts input.parameter_y(2)  # => 4

If it isn’t possible to load the input file into an object’s namespace, the next best thing would be local access to the variables (as long as they aren’t globally visible):

load_input_file
puts parameter_x     # => "10 bytes"
puts parameter_y(2)  # => 4

Is this possible (without manually parsing the input file)?

Answer 1

I think these are your options:

1. Wrap a module around input.rb:

module Input
  CONST = 1
  def meth
   ...
end

But your users will need to add: module Input and end around their code. (Not too much to ask for, is it?)

2. Stringification

Per your own suggestion:
Strinigfy the input.rb file, wrap it with a module, and change the local variables to ivars, then ouput that to a input_modified.rb file:

In this case, it would be much easier if you told your users to prepend an @ before their variable declarations.

require 'fileutils'
require 'tempfile'

inp = 'input.rb'
oup = 'input_modified.rb'
out = Tempfile.new('temp.txt')

File.open(inp, 'r') do |file|
  out.puts "module Input\n" + file.read.gsub("\n","\n\s") + "\nend"
end
FileUtils.mv out.path, oup