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?

Pan Thomakos · Accepted Answer · 2011-02-21 21:55:44Z

5

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

answered Feb 21, 2011 at 21:55

Pan Thomakos

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1 Comment

Xavier Holt Over a year ago

Depending on what sort of object you're talking about, you might be able to get everything you need just with obj.inspect (?).

Miquel · Accepted Answer · 2011-02-21 22:15:16Z

0

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

answered Feb 21, 2011 at 22:15

Miquel

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