What is @controller instance variable?

Rails
1

In a book I’m reading the author tries to do the following from within
his controller test file:

class PagesControllerTest < ActionController::TestCase
def test_create_link_in_index
get :index
assert_select “a[href=?]”, url_for(:action => :new), :text => ‘Neue
Seite’
end
end

However the method ‘url_for’ is unknown within the class
PagesControllerTest, as it is defined in ActionController::Base.

To get around this he writes (although this is not the final solution):

assert_select “a[href=?]”, @controller.url_for(:action => :new,
:only_path => true), :text => ‘Neue Seite’

How is he able to reference a method defined in another class, simply by
prefixing the method call with ‘@controller’

Could someone explain what is ‘@controller’ in this context?

I tried Googling it, but as Google ignores the ‘@’ I couldn’t get very
far.

Thanks in advance

2

On Aug 9, 8:14 pm, Jim B. [email protected] wrote:

assert_select “a[href=?]”, @controller.url_for(:action => :new,
:only_path => true), :text => ‘Neue Seite’

How is he able to reference a method defined in another class, simply by
prefixing the method call with ‘@controller’

Could someone explain what is ‘@controller’ in this context?

it’s an instance of the controller class that you’re testing
(ActionController::TestCase sets one up for you)

Fred

3

Hi Jim,

On Mon, Aug 9, 2010 at 2:14 PM, Jim B. [email protected]
wrote:

How is he able to reference a method defined in another class, simply by
prefixing the method call with ‘@controller’

Could someone explain what is ‘@controller’ in this context?

See Section 4.4 Instance Variables in

HTH,
Bill

4

On 9 August 2010 20:14, Jim B. [email protected] wrote:

Could someone explain what is ‘@controller’ in this context?

I tried Googling it, but as Google ignores the ‘@’ I couldn’t get very
far.

‘@controller’ is an instance variable in ActionController::TestCase.
ActionController::TestCase sets up this variable to contain an
instance of the controller class you are testing (in this case,
PagesController).

In other words, ActionController::TestCase does something like this:

@controller = PagesController.new

which is why you’re able to call PagesController methods on @controller.

(The ‘@’ symbol before a variable in Ruby just means that it is an
instance variable, as opposed to an ordinary local variable.)

Chris

5

On Aug 9, 9:08 pm, Jim B. [email protected] wrote:

ActionController::TestCase containing a reference to my controller
(PagesController).

PagesController inherits from ApplicationController.

ApplicationController inherits from ActionController::Base.

Therefore, in ActionController::TestCase, by prepending a method call
with @controller, owing to the aforementioned class hierarchy, I can
access methods defined in ActionController::Base.

Some of the way you phrased that seems a bit awkward to me. It not
that @controller contains a reference to you controller - it is an
actual instance of it.
And ‘prepending a method call’ sounds like you think there is some
magic going on - there isn’t - methods are always called on a certain
object (omitting the object means the method is called on self)

Fred

6

Hi,

Thanks for all of the replies.
That has really made things a lot clearer for me.

So, to summarize:

‘url_for’ is a method defined in ActionController::Base.

@controller is an instance variable initiated by
ActionController::TestCase containing a reference to my controller
(PagesController).

PagesController inherits from ApplicationController.

ApplicationController inherits from ActionController::Base.

Therefore, in ActionController::TestCase, by prepending a method call
with @controller, owing to the aforementioned class hierarchy, I can
access methods defined in ActionController::Base.

Would that be correct?

Thanks again for your help.

7

It not that @controller contains a reference to you controller -
it is an actual instance of it.

OK, I phrased that badly.

And ‘prepending a method call’ sounds like you think there is some
magic going on - there isn’t - methods are always called on a certain
object (omitting the object means the method is called on self)

And that too :slight_smile:
Thanks for clearing that up.