try ruby online here

class A
  B = "b"
  @@a = 1

  def a 
    @@a
  end
end

Question, how can we use class_eval to reassign the value of B and @@a so that

B = ‘b2’

@@a = 2

 

check the answer 
A.class_eval "@@a = 2"
A.class_eval "B.replace('b2')"

p A.new.a
# => 2

p A::B
#=> 'b2'

   

module B
  def hi
    p 'hi'
  end
end

class C 
  def self.set_logger method_name
  end

  include B

  set_logger :hi
end

Question, how can we do that we don’t need to write the code?

set_logger :hi

in the class C

 

check the answer 
module B
  def self.included base
    base.class_eval do
      set_logger :hi
    end
  end

  def hi
    p 'hi'
  end
end

class C
  def self.set_logger mthode_name
  end

  include B
  set_logger :hi
end