Scan instance variable from controller

Question

Is there any way to read (scan) all the instance variables from the controller's methods?

ex:

I'll define some instance variables in a controller either index or show or custom defined method. I want to know (get) all the instance variable values from one place.

class TestClass
  def t1
    @v1 = "test"
  end

  def t2
    @v2 = "test1"
  end
end

TestClass.instance_variables
 => [] 

tc = TestClass.new
tc.t1
tc.instance_variable_names
=> ["@v1"]

The above code is working for the class with the custom methods not with default methods (index, show, etc..)

Rails.env
=> "development"
u = UsersController.new
 => #<UsersController:0x00000004233990 @_routes=nil, @_action_has_layout=true, @_headers={"Content-Type"=>"text/html"}, @_status=200, @_request=nil, @_response=nil> 
1.9.3p448 :109 > u.index
NoMethodError: undefined method `env' for nil:NilClass

nickcen · Accepted Answer · 2014-06-11 09:59:40Z

1

call the instance_variables() method.

instance_variable_names()

# File activesupport/lib/active_support/core_ext/object/instance_variables.rb, line 27
def instance_variable_names
   instance_variables.map { |var| var.to_s }
end

edited Jun 11, 2014 at 9:59

answered Jun 11, 2014 at 9:50

nickcen

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3 Comments

Mr. Black Over a year ago

Is it working? I am sure it'll not work. Please put your answer with some example.

nickcen Over a year ago

@Mr.Black i get it from the api doc. Not verify it by myself. Hope it can help.

Mr. Black Over a year ago

Thanks. It's working only for the Class with custom methods not a resource methods. I got a duplication of this question. stackoverflow.com/questions/6061489/…

Vakiliy · Accepted Answer · 2014-06-11 10:08:02Z

0

The easiest way will probably be something like this:

a = TestClass.new
after_init = a.instance_variables
a.t1
after_t1 = after_init -  a.instance_variables

answered Jun 11, 2014 at 10:08

Vakiliy

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6 Comments

Mr. Black Over a year ago

Thanks. It's not working with the Actual controller.

Mr. Black Over a year ago

I have list of controllers which will have some unique variable across most of methods with different values. I need to get the value of the particular instance variable and pass to common function.

Vakiliy Over a year ago

I suppose that you used in the controller 'before_action', call these methods manually before performing call 'index','show' ...

Mr. Black Over a year ago

Yes, I thought also. But, seems I can't call the method index or show directly. See my updated question.

Vakiliy Over a year ago

From the example it is clear only that you have some variable that does not have a method 'env'. Show the entire method code

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