ruby - Get all instance variables declared in class

Question

Please help me get all instance variables declared in a class the same way instance_methods shows me all methods available in a class.

class A
  attr_accessor :ab, :ac
end

puts A.instance_methods  #gives ab and ac

puts A.something         #gives me @ab @ac...

Answer 1

You can use instance_variables:

A.instance_variables

but that’s probably not what you want, since that gets the instance variables in the class A, not an instance of that class. So you probably want:

a = A.new
a.instance_variables

But note that just calling attr_accessor doesn’t define any instance variables (it just defines methods), so there won’t be any in the instance until you set them explicitly.

a = A.new
a.instance_variables #=> []
a.ab = 'foo'
a.instance_variables #=> [:@ab]