I am trying to create a null object in my application. I would like to
assigned a null user object for anonymous/ mot-logged-in user, i.e. if
session variable has nil data.
In my User model, I have created a subclass like this:
class UnassignedUser < User
def save
false
end
def update
false
end
def username
"Unassigned"
end
def county_id
"-999"
end
def role_id
"5"
end
end
When I go to console to try out this model following is the
output:>> UnassignedUser.new
NameError: uninitialized constant UnassignedUser
from
/usr/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/active_support/dependencies.rb:278:in
`load_missing_constant''
from
/usr/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/active_support/dependencies.rb:467:in
`const_missing''
from
/usr/lib/ruby/gems/1.8/gems/activesupport-2.1.0/lib/active_support/dependencies.rb:479:in
`const_missing''
from (irb):1
>> User.new
=> #<User id: nil, username: nil, section_id: nil, password_hash: nil,
password_salt: nil, role_id: nil, member_number: nil, tm_zone_info: nil,
region_id: nil>
>> UnassignedUser.new
=> #<UnassignedUser id: nil, username: nil, section_id: nil,
password_hash: nil, password_salt: nil, role_id: nil, member_number:
nil, tm_zone_info: nil, region_id: nil>
If I create user object first and then unassigneduser then it does not
give any error (although it is not doing what I intend to do).
Can anyone please elaborate on how to use null object pattern?
Thanks,
CS.
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If you have a construct like this (all in the same file):
# app/models/user.rb
class User < ActiveRecord::Base
# ...
end
class UnassignedUser < User
def self.shout
puts "yeah"
end
end
script/console will behave like this:
>> UnassignedUser.shout
NameError: uninitialized constant UnassignedUser (...)
>> User
=> User(id: integer, login: string, email: string, password: string,
created_at: datetime, updated_at: datetime)
>> UnassignedUser.shout
yeah
=> nil
UnassignedUser gets only loaded when User is loaded. put it in its own
file and maybe add:
self.abstract_class = true
other than that you can load it whenever you want via include or
require.
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MaD wrote:> If you have a construct like this (all in the same file): > > # app/models/user.rb > class User < ActiveRecord::Base > # ... > end > > class UnassignedUser < User > def self.shout > puts "yeah" > end > end > > script/console will behave like this: > >> UnassignedUser.shout > NameError: uninitialized constant UnassignedUser (...) > >> User > => User(id: integer, login: string, email: string, password: string, > created_at: datetime, updated_at: datetime) > >> UnassignedUser.shout > yeah > => nil > > UnassignedUser gets only loaded when User is loaded. put it in its own > file and maybe add: > self.abstract_class = trueSeparate file in the model directory? My objective is to avoid nil object errors when no user is logged in - i.e. when session[:user] is nil. However, I still need to call some instance methods on this object. Please suggest me how can I do this?> > other than that you can load it whenever you want via include or > require.-- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Hi Carlos, On Sat, 2009-03-14 at 21:30 +0100, Carlos Santana wrote:> My objective is to avoid nil object errors when no user is logged in - > i.e. when session[:user] is nil. > > However, I still need to call some instance methods on this object. > > Please suggest me how can I do this?I''m thinkin'' I must be missin'' somethin''. Why can''t you use... do_somethin'' unless session[:user].nil? ? Best regards, Bill --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
In that case I won''t get any user object. Basically I am trying to implement in my application as mentioned here: http://pivotallabs.com/users/nick/blog/articles/272-access-control-permissions-in-rails For this I have some instance methods in User class. So the ''do_somethin'' is basically not optional (only if user is logged in). So as suggested in the article, I am trying to create a null object. I also looked at acts_as_nullobject plugin: http://martincik.com/?p=22 . But it is giving me some errors. Any help/suggestions are welcome. bill walton wrote:> Hi Carlos, > > On Sat, 2009-03-14 at 21:30 +0100, Carlos Santana wrote: > >> My objective is to avoid nil object errors when no user is logged in - >> i.e. when session[:user] is nil. >> >> However, I still need to call some instance methods on this object. >> >> Please suggest me how can I do this? > > I''m thinkin'' I must be missin'' somethin''. Why can''t you use... > > do_somethin'' unless session[:user].nil? > > ? > > Best regards, > Bill-- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On Mar 14, 8:30 pm, Carlos Santana <rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:> MaD wrote: > > UnassignedUser gets only loaded when User is loaded. put it in its own > > file and maybe add: > > self.abstract_class = true > > Separate file in the model directory? >Yes. The think to understand is that if your app hits the constant Foo, rails will try and load foo.rb hoping that it defines Foo. If there is no such foo.rb because Foo is in fact declared in bar.rb then this don''t work. You need to either put things where rails will find them automatically or explicitly require them (using require_dependency) Fred> My objective is to avoid nil object errors when no user is logged in - > i.e. when session[:user] is nil. > > However, I still need to call some instance methods on this object. > > Please suggest me how can I do this? > > > > > other than that you can load it whenever you want via include or > > require. > > -- > Posted viahttp://www.ruby-forum.com/.--~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
I put UnassignedUser class in a separate file and added self.abstract_class = true and also included requirement of User class. Still same error. Any more guidelines? CS. Frederick Cheung wrote:> On Mar 14, 8:30�pm, Carlos Santana <rails-mailing-l...@andreas-s.net> > wrote: >> MaD wrote: >> > UnassignedUser gets only loaded when User is loaded. put it in its own >> > file and maybe add: >> > � self.abstract_class = true >> >> Separate file in the model directory? >> > > Yes. The think to understand is that if your app hits the constant > Foo, rails will try and load foo.rb hoping that it defines Foo. If > there is no such foo.rb because Foo is in fact declared in bar.rb then > this don''t work. > You need to either put things where rails will find them automatically > or explicitly require them (using require_dependency) > > Fred-- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
It worked.. Had a typo.. :( Thanks for the help. Carlos Santana wrote:> I put UnassignedUser class in a separate file and added > self.abstract_class = true and also included requirement of User class. > Still same error. > > Any more guidelines? > > CS. > > Frederick Cheung wrote: >> On Mar 14, 8:30�pm, Carlos Santana <rails-mailing-l...@andreas-s.net> >> wrote: >>> MaD wrote: >>> > UnassignedUser gets only loaded when User is loaded. put it in its own >>> > file and maybe add: >>> > � self.abstract_class = true >>> >>> Separate file in the model directory? >>> >> >> Yes. The think to understand is that if your app hits the constant >> Foo, rails will try and load foo.rb hoping that it defines Foo. If >> there is no such foo.rb because Foo is in fact declared in bar.rb then >> this don''t work. >> You need to either put things where rails will find them automatically >> or explicitly require them (using require_dependency) >> >> Fred-- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Hello Carlos,
I am glad it worked for you. Access control is a fundamental
requirement along with authentication. Jim Neath''s Bort which is
available on Github, packages Role Requirements written by Tim Harper
along with Restful Authentication for creating a baseline
application. Tim has done an excellent job of implementing a
"minimal" authorization plugin. I am using Bort to develop my own
toolkit for creating applications.
I looked at the article that you list above. It is very well written
and very nice to learn from. The key thing missing from it is that it
fails to deal with Roles and instead deals directly with users. I
think a minimal layer of roles between users and controllers is a key
requirement.
I am not saying that Role Requirement is the only plugin that
addresses it. It is just that it packaged with Bort which has other
key plugins in addition to Restful Authentication and Role
Requirements. Gets the job done.
So instead of saying session[:current_user].nil? you may want to say
[:current_user].has_role?(''anonymous'') for example. See the
method
"has_role?" provided by Role Requirement? That is the key in my
opinion.
I may be wrong, but that is where I am going with this.
Hope this helps.
Bharat
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I have a roles table and I check authorization as:
def can_be_deleted_by?(user)
return false if user.role.nil?
valid_roles = %w{admin creator}
return false unless user.username == self.creuser ||
valid_roles.include?(user.role.name)
return true
end
One other thing I had to modify after using null obect was to check
user.role.nil? before calling user.role.name, which otherwise checks for
nil.name for anonymous user.
The delete action can be performed only by admin or the one who created
that topic/item. Hence I am using roles as well as check by
username(creator).
-
CS.
Bharat Ruparel wrote:> Hello Carlos,
> I am glad it worked for you. Access control is a fundamental
> requirement along with authentication. Jim Neath''s Bort which is
> available on Github, packages Role Requirements written by Tim Harper
> along with Restful Authentication for creating a baseline
> application. Tim has done an excellent job of implementing a
> "minimal" authorization plugin. I am using Bort to develop my
own
> toolkit for creating applications.
> I looked at the article that you list above. It is very well written
> and very nice to learn from. The key thing missing from it is that it
> fails to deal with Roles and instead deals directly with users. I
> think a minimal layer of roles between users and controllers is a key
> requirement.
> I am not saying that Role Requirement is the only plugin that
> addresses it. It is just that it packaged with Bort which has other
> key plugins in addition to Restful Authentication and Role
> Requirements. Gets the job done.
> So instead of saying session[:current_user].nil? you may want to say
> [:current_user].has_role?(''anonymous'') for example. See
the method
> "has_role?" provided by Role Requirement? That is the key in my
> opinion.
> I may be wrong, but that is where I am going with this.
> Hope this helps.
> Bharat
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