Rails 4 Filtering on has_many through associations

Rails
1

Hi All,

I have an issue on filtering a has_many through association. My model is
as
follows

class Group
has_and_belongs_to_many :messages
has_many :tags, through :messages
end

class Message
has_and_belongs_to_many :tags
end

class Tag
has_and_belongs_to_many :messages
end

This gives me the tags for all messages in a group. Groups.first.tags
.
However I want to filter on an attribute in messages
(Message.where(:created => ‘11-11-2014’)) based on which tags should be
retrieved. Is it possible to do this in a has_many though association?
Thanks in advance

Thanks,
Ganesh

2

On 26 November 2014 at 08:40, Ganesh Ranganathan
[email protected] wrote:

class Message
do this in a has_many though association? Thanks in advance
Groups.first.messages.where(:created => ‘11-11-2014’).tags

By the way, if you mean :created_at then this will not work as
created_at includes the time, so to get an exact match on 11-11-2014
it would have to be exactly midnight. You will have to use a time
range, and don’t forget to watch out for the timezone.

Colin

3

On Wed, Nov 26, 2014 at 4:07 PM, Colin L. [email protected] wrote:

Groups.first.messages.where(:created => ‘11-11-2014’).tags

By the way, if you mean :created_at then this will not work as
created_at includes the time, so to get an exact match on 11-11-2014
it would have to be exactly midnight. You will have to use a time
range, and don’t forget to watch out for the timezone.

​Hi Colin,

Thanks for your reply. This won’t work since messages would return an
ActiveRelation there is no tags method on an active relation.

In my actual code I will use a between two days. I just used a direct
equals for simplicity sake​

Thanks,
Ganesh

4

On 26 November 2014 at 11:02, Ganesh Ranganathan
[email protected] wrote:

Hi Colin,

Thanks for your reply. This won’t work since messages would return an
ActiveRelation there is no tags method on an active relation.

You are right of course.

Colin

5

On Wed, Nov 26, 2014 at 3:13 PM, Ganesh M. [email protected]
wrote:

You can do this
has_and_belongs_to_many :messages, → { where(created_at: ‘11-11-2014’) }

or you can use scope which is much better

​Hi Ganesh,

I tried various scope syntaxes but it didn’t work. :frowning:

Can you point me in the right direction,

Thanks,
Ganesh​

6

On Wed, Nov 26, 2014 at 6:49 PM, Colin L. [email protected] wrote:

You are right of course.

​I got the answer from another mailing list. Created a static method on
the
Tag model

def self.for_groupmessages_created_on(group_id,fromdate,todate)
Tag.joins(:messages, :groups).where(
messages: {
created: fromdate…todate
},
groups: {
id: group_id
}

)

Thanks,
Ganesh​