ActiveRecord inner joins

rubyonrails-talk
1

Tim Booher 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

2

Mark Bush wrote:

Tim Booher 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

3

Tim Booher 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.