Relationships problems to access

Rails
1

Hi!
I have an events table, a groups table and invitations table. Invitation
has event_id and group_id. So, Invitation belongs_to event and
belongs_to group.
I have a user table too. User has_many memberships and a membership
belongs_to user and belongs_to group.
So, A user is member of some groups that are invited to events. I want
to know the events that the groups of a user is invited to.
Something like @user.groups.events, but this throws and exception.
Thanks!

2

In User
has_many :groups, :through=>memberships

But use it like this user.groups[0].events. Remember groups is a list.

Khurram Ijaz.
http://www.renai-soft.com

Florencio C. wrote:

Hi!
I have an events table, a groups table and invitations table. Invitation
has event_id and group_id. So, Invitation belongs_to event and
belongs_to group.
I have a user table too. User has_many memberships and a membership
belongs_to user and belongs_to group.
So, A user is member of some groups that are invited to events. I want
to know the events that the groups of a user is invited to.
Something like @user.groups.events, but this throws and exception.
Thanks!

3

I think there isn’t a nice solution at this point,
what you want is;

has_many :events, :through => {:memberships => :groups}

or something,
but I don’t think that works currently,

as a slightly streamlined version of your current method;

def next_events
self.groups.map(&:events).flatten
end

but that may not be efficient, unless you find your user with
User.find(id, :include => {:groups => :events})

alternatively

def next_events
Events.find(:all,
:include => {:group => :user},
:conditions => [“users.id = ?”, self.id]
)
end

but that wont be cached.

personally I’d make a custom scoping

def events_scope
subquery = <<_SQL
SELECT * FROM invitations
INNER JOIN groups ON invitations.group_id = groups.id

    WHERE
        invitations.event_id = events.id
            AND
        EXISTS (
            SELECT * FROM memberships
                INNER JOIN users ON memberships.group_id = groups.id
            WHERE membership.user_id = ?
            )

_SQL
Event.with_scope(
:find => {
:conditions => [subquery, self.id]
}) do
return yield
end
end

def all_events
events_scope do
Event.find(:all)
end
end

but I’m mental in love with with_scope, I guess.

MatthewRudy

Florencio C. wrote:

Hello!
And what if I want to collect all the events from all the groups related
to a user?
I’m using this solution that does not seem very neat:

def next_events
next_events = []
for group in self.groups
for event in group.events
next_events << event
end
end
end

4

Hello!
And what if I want to collect all the events from all the groups related
to a user?
I’m using this solution that does not seem very neat:

def next_events
next_events = []
for group in self.groups
for event in group.events
next_events << event
end
end
end

Khurram Ijaz wrote:

In User
has_many :groups, :through=>memberships

But use it like this user.groups[0].events. Remember groups is a list.

Florencio C. wrote:

Hi!
I have an events table, a groups table and invitations table. Invitation
has event_id and group_id. So, Invitation belongs_to event and
belongs_to group.
I have a user table too. User has_many memberships and a membership
belongs_to user and belongs_to group.
So, A user is member of some groups that are invited to events. I want
to know the events that the groups of a user is invited to.
Something like @user.groups.events, but this throws and exception.
Thanks!

5

Think this plugin does what you want:
http://agilewebdevelopment.com/plugins/nested_has_many_through

seems it might also become part of the rails core in the future…

On 13 Jul., 14:02, Matthew R. [email protected]

6

A correction to my scoping,

Event.with_scope(:find => {
:conditions => [“EXISTS (#{subquery})”, self.id]
}) do
return yield
end

def events_scope
subquery = <<_SQL
SELECT * FROM invitations
INNER JOIN groups ON invitations.group_id = groups.id

    WHERE
        invitations.event_id = events.id
            AND
        EXISTS (
            SELECT * FROM memberships
                INNER JOIN users ON memberships.group_id = groups.id
            WHERE membership.user_id = ?
            )

_SQL
Event.with_scope(
:find => {
:conditions => [subquery, self.id]
}) do
return yield
end
end