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Theodore Mills

2005-Oct-14 15:09 UTC

Fundamental Question

FYI, I''m new to Ruby, so use kid gloves with me.

Given a parent class with a public method:

class ApplicationController < ActionController::Base
def show_left_column (bool)
@show_left_column = bool
end
end

Shouldn''t I be able to call the show_left_column method from a subclass
as
such:

class UserController < ApplicationController
model :user
scaffold :user
show_left_column true
end

I keep getting errors indicating the method cannot be found, but as far I as
I can tell, what I am doing is no different than the model and scaffold
methods.

Can anybody correct my ignorance, please?!

-Theo


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Cuong Tran

2005-Oct-14 15:36 UTC

head link

Re: Fundamental Question

show_left_column is an instance method, which requires an instance of
ApplicationController or subclasses.

On 10/14/05, Theodore Mills
<twmills-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> FYI, I''m new to Ruby, so use kid gloves with me.
>
>  Given a parent class with a public method:
>
>  class ApplicationController < ActionController::Base
>      def show_left_column (bool)
>          @show_left_column = bool
>      end
>  end
>
>  Shouldn''t I be able to call the show_left_column method from a
subclass as
> such:
>
>  class UserController < ApplicationController
>    model :user
>    scaffold :user
>    show_left_column true
>  end
>
>  I keep getting errors indicating the method cannot be found, but as far I
> as I can tell, what I am doing is no different than the model and scaffold
> methods.
>
>  Can anybody correct my ignorance, please?!
>
>  -Theo
>
>
>
>
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>

Matthew Denner

2005-Oct-14 16:09 UTC

head link

Re: Fundamental Question

On 10/14/05, Theodore Mills
<twmills-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>  I keep getting errors indicating the method cannot be found, but as far I
> as I can tell, what I am doing is no different than the model and scaffold
> methods.
What you have defined in your ApplicationController is an instance
method, and what you are calling in your UserController is a class
method, so the errors are correct.

But your problems run slightly deeper than this because, if you simply
change your method definition to:

class ApplicationController < ActionController::Base
    def self.show_left_column (bool)
        @show_left_column = bool
    end
end

Note the ''self'' bit on the method definition, which defines it
as a
class method.

Then this will likely complain too because, in Ruby, @show_left_column
is a declaration of an instance variable, meaning that each instance
of ApplicationController will have it''s own copy (and therefore could
be different from any other).

If you change the code to:

class ApplicationController < ActionController::Base
    def self.show_left_column (bool)
        @@show_left_column = bool
    end
end

Then @@show_left_column is a class variable meaning that all instances
of the ApplicationController will share this value, so it is not
different for each instance.

I probably haven''t explained that at all well but, if you
don''t have
it, I highly recommend the Programming Ruby book
(http://www.pragmaticprogrammer.com/titles/ruby/index.html) as it
*will* teach you Ruby properly.  There''s a copy of the 1st edition
online (http://www.rubycentral.com/book/) but it''s for pre-1.8
versions of Ruby so is a little out-of-date.  If you look at the
"Class Variables and Class Methods" section on
http://www.rubycentral.com/book/tut_classes.html you''ll get an idea of
what I''m trying to say about your problem.

Matt

Nick Sieger

2005-Oct-14 16:34 UTC

head link

Re: Fundamental Question

>
> FYI, I''m new to Ruby, so use kid gloves with me.
>
> Given a parent class with a public method:
>
> class ApplicationController < ActionController::Base
> def show_left_column (bool)
> @show_left_column = bool
> end
> end
>
> Shouldn''t I be able to call the show_left_column method from a
subclass as
> such:
>
> class UserController < ApplicationController
> model :user
> scaffold :user
> show_left_column true
> end
>
> I keep getting errors indicating the method cannot be found, but as far I
> as I can tell, what I am doing is no different than the model and scaffold
> methods.
>
> Can anybody correct my ignorance, please?!

You''ve defind show_left_column as an instance method of
ApplicationController but you are calling it in the class context in
UserController. What you probably want is a class method assigning a value
to a class variable:

class ApplicationController < ActionController::Base
def self.show_left_column(bool)
@@show_left_column = bool
end


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Theodore Mills

2005-Oct-14 16:53 UTC

head link

Re: Fundamental Question

Nick,

Now the method is getting found, thanks.

However, that variable (whether instance or class) is not available to my
view, for some reason. Any ideas?

Thanks again!

-Theo



On 10/14/05, Nick Sieger
<nicksieger-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
> FYI, I''m new to Ruby, so use kid gloves with me.
> >
> > Given a parent class with a public method:
> >
> > class ApplicationController < ActionController::Base
> > def show_left_column (bool)
> > @show_left_column = bool
> > end
> > end
> >
> > Shouldn''t I be able to call the show_left_column method from
a subclass
> > as such:
> >
> > class UserController < ApplicationController
> > model :user
> > scaffold :user
> > show_left_column true
> > end
> >
> > I keep getting errors indicating the method cannot be found, but as
far
> > I as I can tell, what I am doing is no different than the model and
scaffold
> > methods.
> >
> > Can anybody correct my ignorance, please?!
>
>
> You''ve defind show_left_column as an instance method of
> ApplicationController but you are calling it in the class context in
> UserController. What you probably want is a class method assigning a value
> to a class variable:
>
> class ApplicationController < ActionController::Base
> def self.show_left_column(bool)
> @@show_left_column = bool
> end
>
>
>
>
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>

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Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
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Theodore Mills

2005-Oct-14 19:12 UTC

head link

Re: Fundamental Question

Thanks a lot, Matt.

I''ve gotten by the first hurdle, now my question seems to be more
Rails-related.

I had thought all instance variables in Controller were automatically
propogated to the View, but that doesn''t seem to be the case. In this
case,
I want all subclasses to inherit certain properties without me having to
redefine them in each subclass. For instance, I want all administrative
pages (such as user) to display a left column.

I read this:

The view has access to the instance-variables of the controller. It''s a
lot
like they are friend classes in that the instance-data simply is available
in the view templates, as if it were in the same scope.

But that doesn''t seem to be true. So my questions is, how do I get the
view
to see my instance variables?

Thanks!

-Theo



On 10/14/05, Matthew Denner
<matt.denner-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
> On 10/14/05, Theodore Mills
<twmills-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > I keep getting errors indicating the method cannot be found, but as
far
> I
> > as I can tell, what I am doing is no different than the model and
> scaffold
> > methods.
>
> What you have defined in your ApplicationController is an instance
> method, and what you are calling in your UserController is a class
> method, so the errors are correct.
>
> But your problems run slightly deeper than this because, if you simply
> change your method definition to:
>
> class ApplicationController < ActionController::Base
> def self.show_left_column (bool)
> @show_left_column = bool
> end
> end
>
> Note the ''self'' bit on the method definition, which
defines it as a
> class method.
>
> Then this will likely complain too because, in Ruby, @show_left_column
> is a declaration of an instance variable, meaning that each instance
> of ApplicationController will have it''s own copy (and therefore
could
> be different from any other).
>
> If you change the code to:
>
> class ApplicationController < ActionController::Base
> def self.show_left_column (bool)
> @@show_left_column = bool
> end
> end
>
> Then @@show_left_column is a class variable meaning that all instances
> of the ApplicationController will share this value, so it is not
> different for each instance.
>
> I probably haven''t explained that at all well but, if you
don''t have
> it, I highly recommend the Programming Ruby book
> (http://www.pragmaticprogrammer.com/titles/ruby/index.html) as it
> *will* teach you Ruby properly. There''s a copy of the 1st edition
> online (http://www.rubycentral.com/book/) but it''s for pre-1.8
> versions of Ruby so is a little out-of-date. If you look at the
> "Class Variables and Class Methods" section on
> http://www.rubycentral.com/book/tut_classes.html you''ll get an
idea of
> what I''m trying to say about your problem.
>
> Matt
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>

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Rails mailing list
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Nick Sieger

2005-Oct-14 19:16 UTC

head link

Re: Fundamental Question

>
>
> Now the method is getting found, thanks.
>
> However, that variable (whether instance or class) is not available to my
> view, for some reason. Any ideas?


You probably want an accessor method like

class AplicationController < ActionController::Base
# ...
def self.show_left_column?
@@show_left_column
end
end

then in your view you would have

<% if controller.class.show_left_column? %>
... left column here ...
<% end %>

HTH
/Nick


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Rails mailing list
Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
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Nick Sieger

2005-Oct-14 19:17 UTC

head link

Re: Fundamental Question

>
>
> Now the method is getting found, thanks.
>
> However, that variable (whether instance or class) is not available to my
> view, for some reason. Any ideas?


You probably want an accessor method like

class AplicationController < ActionController::Base
# ...
def self.show_left_column?
@@show_left_column
end
end

then in your view you would have

<% if controller.class.show_left_column? %>
... left column here ...
<% end %>

HTH
/Nick


_______________________________________________
Rails mailing list
Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
http://lists.rubyonrails.org/mailman/listinfo/rails

Nick Sieger

2005-Oct-14 19:31 UTC

head link

Re: Fundamental Question

>
>
> Now the method is getting found, thanks.
>
> However, that variable (whether instance or class) is not available to my
> view, for some reason. Any ideas?


You probably want an accessor method like

class AplicationController < ActionController::Base
# ...
def self.show_left_column?
@@show_left_column
end
end

then in your view you would have

<% if controller.class.show_left_column? %>
... left column here ...
<% end %>

HTH
/Nick


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Rails mailing list
Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
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Theodore Mills

2005-Oct-14 19:35 UTC

head link

Re: Fundamental Question

Kick ass, thanks for the tip!

I didn''t realize there was a global controller variable available to
the
template.

It works!

On 10/14/05, Nick Sieger
<nicksieger-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
>
> > Now the method is getting found, thanks.
> >
> > However, that variable (whether instance or class) is not available to
> > my view, for some reason. Any ideas?
>
>
>
> You probably want an accessor method like
>
> class AplicationController < ActionController::Base
> # ...
> def self.show_left_column?
> @@show_left_column
> end
> end
>
> then in your view you would have
>
> <% if controller.class.show_left_column? %>
> ... left column here ...
> <% end %>
>
> HTH
> /Nick
>
>
>
>
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>

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Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
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Ezra Zygmuntowicz

2005-Oct-14 20:47 UTC

head link

Re: Fundamental Question

Matt-
     The instance variables that your view has automatic access to  
have to be in the action in your controller. Like so:

class MyController < ApplicationController

@another_instance_var_not_in_the_action_that_you_are_calling

def index
     @left_column = LeftColumn.find :all, :conditions => "whatever =  
something"
     @posts = Post.find(params[:id}
     @categories = Category.find :all
end

end


     So in your index.rhtml view file you will have access to:  
@left_column, @posts and @categories. But you won''t have access to :  
@another_instance_var_not_in_the_action_that_you_are_calling

HTH-
-Ezra

On Oct 14, 2005, at 12:12 PM, Theodore Mills wrote:
> Thanks a lot, Matt.
>
> I''ve gotten by the first hurdle, now my question seems to be more
> Rails-related.
>
> I had thought all instance variables in Controller were  
> automatically propogated to the View, but that doesn''t seem to be
> the case. In this case, I want all subclasses to inherit certain  
> properties without me having to redefine them in each subclass.   
> For instance, I want all administrative pages (such as user) to  
> display a left column.
>
> I read this:
>
> The view has access to the instance-variables of the controller.  
> It''s a lot like they are friend classes in that the instance-data
> simply is available in the view templates, as if it were in the  
> same scope.
>
> But that doesn''t seem to be true. So my questions is, how do I get
> the view to see my instance variables?
>
> Thanks!
>
> -Theo
>
>
>
> On 10/14/05, Matthew Denner
<matt.denner-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: On
> 10/14/05, Theodore Mills
<twmills-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >  I keep getting errors indicating the method cannot be found, but  
> as far I
> > as I can tell, what I am doing is no different than the model and  
> scaffold
> > methods.
>
> What you have defined in your ApplicationController is an instance
> method, and what you are calling in your UserController is a class
> method, so the errors are correct.
>
> But your problems run slightly deeper than this because, if you simply
> change your method definition to:
>
> class ApplicationController < ActionController::Base
>     def self.show_left_column (bool)
>         @show_left_column = bool
>     end
> end
>
> Note the ''self'' bit on the method definition, which
defines it as a
> class method.
>
> Then this will likely complain too because, in Ruby, @show_left_column
> is a declaration of an instance variable, meaning that each instance
> of ApplicationController will have it''s own copy (and therefore
could
> be different from any other).
>
> If you change the code to:
>
> class ApplicationController < ActionController::Base
>     def self.show_left_column (bool)
>         @@show_left_column = bool
>     end
> end
>
> Then @@show_left_column is a class variable meaning that all instances
> of the ApplicationController will share this value, so it is not
> different for each instance.
>
> I probably haven''t explained that at all well but, if you
don''t have
> it, I highly recommend the Programming Ruby book
> (http://www.pragmaticprogrammer.com/titles/ruby/index.html) as it
> *will* teach you Ruby properly.  There''s a copy of the 1st edition
> online (http://www.rubycentral.com/book/) but it''s for pre-1.8
> versions of Ruby so is a little out-of-date.  If you look at the
> "Class Variables and Class Methods" section on
> http://www.rubycentral.com/book/tut_classes.html you''ll get an
idea of
> what I''m trying to say about your problem.
>
> Matt
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
-Ezra Zygmuntowicz
Yakima Herald-Republic
WebMaster
http://yakimaherald.com
509-577-7732
ezra-gdxLOakOTQ9oetBuM9ipNAC/G2K4zDHf@public.gmane.org

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