Questions on scopes

Hey Group,

I am trying to use [what I thought should be] a simple scope for a message object

   scope :unread, where(:read_at => nil)

where the read_at attribute is of type datetime

This is causing the scope to trip a no method error when called upon.

I have a helper method which contains :

if message.read_at == nil
       "NEW"
end

and that works fine. however even

  scope :unread, where("read_at == ?", nil )

does not seem to want to work.

I know I must be missing something terribly obvious about this. Any kick in the right direction is appreciated.

Thanks

Jesse

Hey Group,

I am trying to use [what I thought should be] a simple scope for a
message object

scope :unread, where(:read_at => nil)

where the read_at attribute is of type datetime

This is causing the scope to trip a no method error when called upon.

I have a helper method which contains :

if message.read_at == nil
"NEW"
end

and that works fine. however even

scope :unread, where("read_at == ?", nil )

When comparing with nil you have to use IS NULL rather than the usual
comparison operator. where(:read_at => nil) should work though. How
are you using the scope?

Fred


Hey Group,
I am trying to use [what I thought should be] a simple scope for a
message object
   scope :unread, where(:read_at => nil)
where the read_at attribute is of type datetime
This is causing the scope to trip a no method error when called upon.
I have a helper method  which contains :
if message.read_at == nil
       "NEW"
end
and that works fine. however even
  scope :unread, where("read_at == ?", nil )
When comparing with nil you have to use IS NULL rather than the usual
comparison operator. where(:read_at => nil) should work though. How
are you using the scope?
I am making a call to it through

current_user.received_messages.unread.length which trips a MYSQL
Error

Mysql2::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '== NULL)' at line 1: SELECT `message_copies`.* FROM `message_copies` WHERE (`message_copies`.recipient_id = 1) AND (read_at == NULL)

Sorry I figured out the other issue.

is that using where("read_at == ?", nil ) ? That's just invalid
syntax, since the comparison operator operator is = in SQL. NULL is a
special case though - use IS NULL/IS NOT NULL to test for null values.

Fred

When comparing with nil you have to use IS NULL rather than the usual
comparison operator. where(:read_at => nil) should work though. How
are you using the scope?

I am making a call to it through
current_user.received_messages.unread.length which trips a MYSQL Error

>Mysql2::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '== NULL)' at line 1: SELECT `message_copies`.* FROM `message_copies` WHERE (`message_copies`.recipient_id = 1) AND (read_at == NULL)|

is that using where("read_at == ?", nil ) ? That's just invalid
syntax, since the comparison operator operator is = in SQL. NULL is a
special case though - use IS NULL/IS NOT NULL to test for null values.

Thanks, that did the trick.