Rails 4 Filtering on has_many through associations

[Ganesh Ranganathan]

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

[Colin Law]

On 26 November 2014 at 08:40, Ganesh Ranganathan

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

>
> Thanks,
> Ganesh
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[Ganesh Ranganathan]

On Wed, Nov 26, 2014 at 4:07 PM, Colin Law <cla...@gmail.com> 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

[Ganesh Ranganathan]

On Wed, Nov 26, 2014 at 3:13 PM, Ganesh Mohan <ganesh...@gmail.com> 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. :(

Can you point me in the right direction, 

Thanks,

Ganesh​

[Colin Law]

On 26 November 2014 at 11:02, Ganesh Ranganathan

<ganesh.ran...@gmail.com> wrote:
>
> On Wed, Nov 26, 2014 at 4:07 PM, Colin Law <cla...@gmail.com> 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.

You are right of course.

Colin

[Ganesh Ranganathan]

On Wed, Nov 26, 2014 at 6:49 PM, Colin Law <cla...@gmail.com> 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​