I have the following models:
class Event < ActiveRecord::Base
has_many :action_items
end
class ActionItem < ActiveRecord::Base
belongs_to :event
belongs_to :action_item_type
end
class ActionItemType < ActiveRecord::Base
has_many :action_items
end
And what I want to do is, for a given event, find all the action items that have an action item type with a name of "foo" (for example). So I think the SQL would go something like this:
SELECT * FROM action_items a
INNER JOIN action_item_types t
ON a.action_item_type_id = t.id
WHERE a.event_id = 1
AND t.name = "foo"
Can anybody help me translate this into a nice active record query? (Rails 3 - Arel)
Thanks!
Well I think I solved it myself. Here's what I did
e = Event.find(1)
e.action_items.joins(:action_item_type).where("action_item_types.name = ?", "foo")
Ehm, why not define
has_many :action_item_types, :through => :action_items
and refer to
e.action_item_types.where(:name => "foo")
?
or (as long as "name" is a unique column name)
e.action_items.joins(:action_item_type).where(:name => "foo")
Related
My Customer and Person models looks like this:
class Customer < ActiveRecord::Base
belongs_to :person
belongs_to :company
end
class Person < ActiveRecord::Base
has_one :customer
end
How can I get all Person records that have an association with a Customer?
with sql it might be something like
Customer.where("customers.person_id IS NOT NULL")
to get Person record you can use join
Person.joins( :customers ).where("customers.person_id IS NOT NULL")
I'm not sue either where is necessary here (I believe no) so try Person.joins( :customers ) first
person_array = []
Person.all.each do |p|
unless p.customer.nil?
person_array << p
end
end
I don't think it's the fastest query but:
Customer.where('person_id IS NOT NULL').map(&:person)
rails 2.3.x
Customer.all(:include => :person).map(&:person).compact
I don't seem to get this right for some reason, though it sounds simple :/
I have three models :
User(id,name,email)
Skill(id,name,description)
UserSkill(user_id,skill_id,level)
How can i get all skills of a certain user, whether he or she has discovered them or not ?
For example, 3 skills (walk, talk, write). 3 users (John, Mary, Jack).
If Mary walks and writes, how can i get it back as a result like :
Mary => {Skill: walk(includes UserSkill), Skill : talk, Skill : write(includes UserSkill) }
You get the idea :)
Try this:
class User
def skill_list
Skill.all(
:select =>"skills.*, A.user_id AS user_id",
:joins => "LEFT OUTER JOIN user_skills A
ON A.skill_id = skills.id
AND A.user_id = #{id}").map do |skill|
skill.name + (skill.user_id.nil? ? "" : "(*)")
end
end
end
Now
user = User.find_by_name("Mary")
user.skill_list
Will print:
[
walk(*),
talk,
write(*)
]
I'm assuming you want to set something up like this:
class User < ActiveRecord::Base
has_many :user_skills
has_many :skills, :through => :user_skills
end
class Skill < ActiveRecord::Base
has_many :user_skills
has_many :users, :through => :user_skills
end
class UserSkill < ActiveRecord::Base
belongs_to :user
belongs_to :skill
end
then you can do:
my_user.skills # returns all Skill records assigned to the user
my_user.user_skills.includes(:skill) # this allows you to access :level in addition to Skill attributes
So the way to get both skills and user_skills is to use the :user_skills association. Basic has_many :through. Am I missing something?
user = User.first
user.user_skills.all.map(&:skills)
I am trying to use update_all through an association, and i am getting mysql errors, anyone know why please?
class Basket < ActiveRecord::Base
has_many :basket_items
has_many :articles, :through => :basket_items
def activate_articles
articles.update_all :active => true
end
end
class BasketItem < ActiveRecord::Base
belongs_to :basket
belongs_to :item
belongs_to :article
end
Mysql::Error: Unknown column 'basket_items.basket_id' in 'where clause': UPDATE `articles` SET `active` = 1 WHERE ((`basket_items`.basket_id = 114))
http://dev.rubyonrails.org/ticket/5353
Looks like there was a problem with n-n associations using has_many :through and using update all. Nothing seems to have been done.
1-n associations do appear to work.
Bug?
dev.rubyonrails moved it's tickets to github's issue tracker. Here is the moved link: https://github.com/rails/rails/issues/522
#nolman posted this help on the ticket
#daicoden and I at #square were pairing on this and we were able to put something together along the lines of:
class Comment
class << self
def trash_all
sql = "UPDATE #{quoted_table_name} "
add_joins!(sql, {})
sql << "SET #{sanitize_sql_for_assignment({:trashed => true})} "
add_conditions!(sql, {})
connection.execute(sql)
end
end
end
Now you can call todolist.comments(:conditions => {:trashed => false}).trash_all
This results in the following SQL:
UPDATE `comments` INNER JOIN `todos` ON `todos`.id = `comments`.todo_id SET `trashed` = 1 WHERE (`comments`.`trashed` = 0 AND `todos`.`todolist_id` = 968316918)
Hope this helps!
I am putting together a messaging system for a rails app I am working on.
I am building it in a similar fashion to facebook's system, so messages are grouped into threads, etc.
My related models are:
MsgThread - main container of a thread
Message - each message/reply in thread
Recipience - ties to user to define which users should subscribe to this thread
Read - determines whether or not a user has read a specific message
My relationships look like
class User < ActiveRecord::Base
#stuff...
has_many :msg_threads, :foreign_key => 'originator_id' #threads the user has started
has_many :recipiences
has_many :subscribed_threads, :through => :recipiences, :source => :msg_thread #threads the user is subscribed to
end
class MsgThread < ActiveRecord::Base
has_many :messages
has_many :recipiences
belongs_to :originator, :class_name => "User", :foreign_key => "originator_id"
end
class Recipience < ActiveRecord::Base
belongs_to :user
belongs_to :msg_thread
end
class Message < ActiveRecord::Base
belongs_to :msg_thread
belongs_to :author, :class_name => "User", :foreign_key => "author_id"
end
class Read < ActiveRecord::Base
belongs_to :user
belongs_to :message
end
I'd like to create a new selector in the user sort of like:
has_many :updated_threads, :through => :recipiencies, :source => :msg_thread, :conditions => {THREAD CONTAINS MESSAGES WHICH ARE UNREAD (have no 'read' models tying a user to a message)}
I was thinking of either writing a long condition with multiple joins, or possibly writing giving the model an updated_threads method to return this, but I'd like to see if there is an easier way first. Am I able to pass some kind of nested hash into the conditions instead of a string?
Any ideas? Also, if there is something fundamentally wrong with my structure for this functionality let me know! Thanks!!
UPDATE:
While I would still appreciate input on better possibilities if they exist, this is what I have gotten working now:
class User < ActiveRecord::Base
# stuff...
def updated_threads
MsgThread.find_by_sql("
SELECT msg_threads.* FROM msg_threads
INNER JOIN messages ON messages.msg_thread_id = msg_threads.id
INNER JOIN recipiences ON recipiences.msg_thread_id = msg_threads.id
WHERE (SELECT COUNT(*) FROM `reads` WHERE reads.message_id = messages.id AND reads.user_id = #{self.id}) = 0
AND (SELECT COUNT(*) FROM recipiences WHERE recipiences.user_id = #{self.id} AND recipiences.msg_thread_id = msg_threads.id) > 0
")
end
end
Seems to be working fine!
Also to check if a specific thread (and message) are read:
class Message < ActiveRecord::Base
# stuff...
def read?(user_id)
Read.exists?(:user_id => user_id, :message_id => self.id)
end
end
class MsgThread < ActiveRecord::Base
# stuff...
def updated?(user_id)
updated = false
self.messages.each { |m| updated = true if !m.read?(user_id) }
updated
end
end
Any suggestions to improve this?
Add a named_scope to the MsgThread model:
class MsgThread < ActiveRecord::Base
named_scope :unread_threads, lambda { |user|
{
:include => [{:messages=>[:reads]}, recipiencies],
:conditions => ["recipiences.user_id = ? AND reads.message_id IS NULL",
user.id],
:group => "msg_threads.id"
}}
end
Note: Rails uses LEFT OUTER JOIN for :include. Hence the IS NULL check works.
Now you can do the following:
MsgThread.unread_threads(current_user)
Second part can be written as:
class Message
has_many :reads
def read?(usr)
reads.exists?(:user_id => usr.id)
end
end
class MsgThread < ActiveRecord::Base
def updated?(usr)
messages.first(:joins => :reads,
:conditions => ["reads.user_id = ? ", usr.id]
) != nil
end
end
You might want to take a look at Arel, which can help with complex SQL queries. I believe (don't quote me) this is already baked into Rails3.
I was wondering if it was possible to use the find method to order the results based on a class's has_many relationship with another class. e.g.
# has the columns id, name
class Dog < ActiveRecord::Base
has_many :dog_tags
end
# has the columns id, color, dog_id
class DogTags < ActiveRecord::Base
belongs_to :dog
end
and I would like to do something like this:
#result = DogTag.find(:all, :order => dog.name)
thank you.
In Rails 4 it should be done this way:
#result = DogTag.joins(:dog).order('dogs.name')
or with scope:
class DogTags < ActiveRecord::Base
belongs_to :dog
scope :ordered_by_dog_name, -> { joins(:dog).order('dogs.name') }
end
#result = DogTags.ordered_by_dog_name
The second is easier to mock in tests as controller doesn't have to know about model details.
You need to join the related table to the request.
#result = DogTag.find(:all, :joins => :dog, :order => 'dogs.name')
Note that dogs is plural in the :order statement.