Rails - Aug 2006 - Clarification on error_messages_for

Just learning Rails.. So this is probably a noob question.  My apologies.
Could anyone please give me a quick summary/example on the usage of
error_messages_for?

I have two tables/models, Group and GroupMembers.  Obviously, a Group
has_many GroupMembers.  I have a customized view which shows a list of
GroupMembers followed by a field and a button which facilitates adding a
member to the group by either email address or login.

When the user attempts to add someone to the group who is already there, I
need to return to this EditMembers view with an error message.

I cannot figure out how to use error_messages_for to display the error
message when returning to the view.  The most natural thing to attach the
messages to seems to be the GroupMember object, but the new groupmember
object doesn''t exist until the button action and not on the first view
of
the groupmembers list, so I get a reference to a nil object.

If anyone could provide me with some pseudocode of how it should work, that
would be great!  Thanks!
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
http://wrath.rubyonrails.org/pipermail/rails/attachments/20060809/093328b3/attachment.html

Without delving specifically into your situation, remember that  
ActiveRecord::new creates an object without saving it to the  
database.  So even if you don''t have parameters to create a new  
object, you can create an empty model to avoid the nil problem.

On Aug 9, 2006, at 4:09 PM, Gene Horodecki wrote:
> Just learning Rails.. So this is probably a noob question.  My  
> apologies.  Could anyone please give me a quick summary/example on  
> the usage of error_messages_for?
>
> I have two tables/models, Group and GroupMembers.  Obviously, a  
> Group has_many GroupMembers.  I have a customized view which shows  
> a list of GroupMembers followed by a field and a button which  
> facilitates adding a member to the group by either email address or  
> login.
>
> When the user attempts to add someone to the group who is already  
> there, I need to return to this EditMembers view with an error  
> message.
>
> I cannot figure out how to use error_messages_for to display the  
> error message when returning to the view.  The most natural thing  
> to attach the messages to seems to be the GroupMember object, but  
> the new groupmember object doesn''t exist until the button action  
> and not on the first view of the groupmembers list, so I get a  
> reference to a nil object.
>
> If anyone could provide me with some pseudocode of how it should  
> work, that would be great!  Thanks!
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails