Search code examples
crystal-lang

Method argument of an unknown type

I'm trying to write a utility library which tries to call a method on an arbitrary object type. In ruby, I'd do something like:

def foo(object)
  object.public_send(:bar)
rescue NoMethodError
  raise "Method not defined on object"
end

foo(instance_of_my_arbitrary_class)

I'm not sure how to do this in Crystal, as the type us unknown so I get a compiler error of Can't infer the type of instance variable 'object'.

How do I accomplish this without knowing the type of the object which will be passed?

Solution

  • I think I figured this out after by utilizing a module and including it.

    module ArbitraryObject; end

class Arbitrary
  include ArbitraryObject
end

class MyLib
  def foo(object : ArbitraryObject)
    ... Code here ...
  end
end

MyLib.new(Arbitrary.new).foo