Rails - Feb 2006 - don''t destroy last user

How would I stop the last user being deleted.
The following code doesn''t work.


before_destroy :dont_destroy_last_user

# Don''t delete user if it the last one
def dont_destroy_last_User
    raise "Can''t destroy last user" if User.length < 1
end

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On 18-feb-2006, at 18:30, Alexander wrote:
> How would I stop the last user being deleted.
> The following code doesn''t work.
before_destroy :check_if_last_user

private
   def check_if_last_user
     raise "Last user can''t be deleted" if self.class.count
== 1
   end

Alexander wrote:
> How would I stop the last user being deleted.
> The following code doesn''t work.
> 
> 
> before_destroy :dont_destroy_last_user
> 
> # Don''t delete user if it the last one
> def dont_destroy_last_User
>     raise "Can''t destroy last user" if User.length <
1
> end
Change to:
> # Don''t delete user if it the last one
> def dont_destroy_last_User
>     raise "Can''t destroy last user" if User.count == 1
> end
Untested,but should work

joey__


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Julian ''Julik'' Tarkhanov wrote:
> On 18-feb-2006, at 18:30, Alexander wrote:
> 
>> How would I stop the last user being deleted.
>> The following code doesn''t work.
> 
> before_destroy :check_if_last_user
> 
> private
>    def check_if_last_user
>      raise "Last user can''t be deleted" if
self.class.count == 1
>    end
Thanks

Also ''raise'' creates quite a ugly error message. Is there any
way of
redirecting and using flash instead?

Alex

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On 18-feb-2006, at 19:06, Alexander wrote:
> Julian ''Julik'' Tarkhanov wrote:
>> On 18-feb-2006, at 18:30, Alexander wrote:
>>
>>> How would I stop the last user being deleted.
>>> The following code doesn''t work.
>>
>> before_destroy :check_if_last_user
>>
>> private
>>    def check_if_last_user
>>      raise "Last user can''t be deleted" if
self.class.count == 1
>>    end
>
> Thanks
>
> Also ''raise'' creates quite a ugly error message. Is there
any way of
> redirecting and using flash instead?

I think the neat way would be with an exception catcher

in the model:

class LastUserCantBeDeleted < RuntimeError; end;

.... raise LastUserCantBeDeleted if self.class.count == 1


in the controller

begin
   @user.destroy!
rescue LastUserCantBeDeleted
   flash[:error] = "This is the last one''
   redirect_to :referer # or something like that
end

A less neat way would be to return false from the method and thus  
stop the callback chain, and then


unless @user.destroy!
   flash[:error] = "This is the last one"
   # ... etc
end

Julian ''Julik'' Tarkhanov wrote:
> class LastUserCantBeDeleted < RuntimeError; end;
> 
> .... raise LastUserCantBeDeleted if self.class.count == 1
> 
> 
> in the controller
> 
> begin
>   @user.destroy!
> rescue LastUserCantBeDeleted
>   flash[:error] = "This is the last one''
>   redirect_to :referer # or something like that
> end
> 
> A less neat way would be to return false from the method and thus stop
> the callback chain, and then
> 
> 
> unless @user.destroy!
>   flash[:error] = "This is the last one"
>   # ... etc
> end
This will not work if you have two independent FCGI/SCGI processes trying
to delete the last user at the same time. Might sound bit extreme, but its
quite possible for example if the user clicks rapidly the submit button twice.

You''ll need to wrap the deletion and the counting of users in a
transaction. The first beta release of AWDWR had similar code for
preventing the deletion of the last administrator. Revised version was
simpler not allowing to delete ''Dave'' user. That''s
another alternative.


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