ActiveRecord inner joins

Rails
#1

I have these models:

User -> Order -> Registration <- Camp

So a user has many orders, orders have many registrations and camps have
many registrations.

I have all the associations written up correctly, but I want to know how
to get all the users for a particular camp.

i.e.

@camp = Camp.find_by_name(“band camp”)
mycampers = @camp.orders.registrations.users

naturally, this doesn’t work – do i have to use sql here? the :include
option to find looks good, but I can’t get it to work.

best,

tim

#2

Tim B. wrote:

i.e.

@camp = Camp.find_by_name(“band camp”)
mycampers = @camp.orders.registrations.users

naturally, this doesn’t work – do i have to use sql here? the :include
option to find looks good, but I can’t get it to work.

Something like

User.find :all, :select => ‘distinct users.*’,
:joins => {:orders => {:registrations => :camp}},
:conditions => [‘camps.name = ?’, camp_name]

–
We develop, watch us RoR, in numbers too big to ignore.

#3

Tim B. wrote:

User -> Order -> Registration <- Camp

So a user has many orders, orders have many registrations and camps have
many registrations.

I have all the associations written up correctly, but I want to know how
to get all the users for a particular camp.

class Camp < ActiveRecord::Base
has_many :registrations
has_many :orders, :through => :registrations, :uniq => true, :include
=> :user
:

@camp = Camp.find_by_name(“band camp”)
mycampers = @camp.orders.map {|o| o.user}.uniq

#4

Mark B. wrote:

Tim B. wrote:

User -> Order -> Registration <- Camp

So a user has many orders, orders have many registrations and camps have
many registrations.

I have all the associations written up correctly, but I want to know how
to get all the users for a particular camp.

class Camp < ActiveRecord::Base
has_many :registrations
has_many :orders, :through => :registrations, :uniq => true, :include
=> :user
:

@camp = Camp.find_by_name(“band camp”)
mycampers = @camp.orders.map {|o| o.user}.uniq

this is great! thanks for your help. is :uniq a custom method of
has_many :through ?

best,

tim

#5

Tim B. wrote:

this is great! thanks for your help. is :uniq a custom method of
has_many :through ?

You can use “:uniq => true” for any “has_many” (and HABTM) association,
however it is most useful for “:through” types since direct associations
that need to be unique collections can be handled in the model
validation to prevent duplicates in the first place.