Question

My code looks something like this

class MyController

  def my_action
    #params hash gets passed here
      ...

    logger.debug "PARAMS >> #{params.inspect}" #first inspect

    @a = MyModule::MyClass.new(params).my_func #some operations done with the argument

    logger.debug "PARAMS >> #{params.inspect}" #second inspect

  end

end

My problem is, the params hash in the ‘second inspect’ is different from the one in the ‘first inspect’. When the params hash is passed in the class’ initializer, some more key value pairs added to it, and when I do the ‘second inspect’ on params I find the same key value pairs in it too! How is this possible? I even tried passing a separate variable that contains the action’s params hash, but in vain!

first inspect : {"action"=>"report", "controller"=>"member/monitoring", "offset"=>"0"}

second inspect : {"new_key1"=>"new_val1", "action"=>"report", "controller"=>"member/monitoring","new_key2"=>"new_val2", "new_key3"=>"new_val3", "offset"=>"0"}

The new_key* are added inside the class, but they turn up in the action’s params hash too.

Answer 1

Values passed as parameters to a method are by reference in Ruby, not by value. As such, they can be descructive and can change your hash. You can easily fix this by using params.dup as the argument to your new method.

Edit: As mu pointed out, it is more appropriate to actually let the new method itself do the dup, instead of duping before passing params.