ruby debugging, attempting to loop through an objects instance variables

Question

I am curious if as to whether or not it would be possible to loop through the instance variables of an object and dump out some basic debug information.

I know you can get a list of instance variables by doing object.instance_variables which returns an array of symbolized variables like [:@var1, :@var2, :@etc] My first guess at how to do this was:

obj.instance_variables.each do
  obj.instance_variable_get(var).to_yaml
end

but i am getting the following error: "can't dump anonymous class Class". What might a better approach be?

Answer 1

The problem is you have some anonymous proc or function in your instance variables that doesn't respond to to_yaml. Because it can't be converted to yaml you are getting this error. Try using inspect instead, all objects should respond to inspect:

obj.instance_variables.each do |var|
  p obj.instance_variable_get(var).inspect
end

Answer 2

You have to take into account that in ruby just declaring the attr_accessor will not create the variable, you need to assign it:

class A
  attr_accessor :x, :y

  def initialize(z)
    @x=z
  end

end

def inspect_object(o)
    o.instance_variables.each do |var|
        var.slice!(0)
        p var
        p o.send(var)
    end

end

a = A.new(5)
inspect_object(a)

This outputs

"x"
5