I have a data model something like this:
# columns include collection_item_id, collection_id, item_id, position, etc
class CollectionItem < ActiveRecord::Base
self.primary_key = 'collection_item_id'
belongs_to :collection
belongs_to :item
end
class Item < ActiveRecord::Base
has_many :collection_items
has_many :collections, :through => :collection_items, :source => :collection
end
class Collection < ActiveRecord::Base
has_many :collection_items, :order => :position
has_many :items, :through => :collection_items, :source => :item, :order => :position
end
An Item can appear in multiple collections and also more than once in the same collection at different positions.
I'm trying to create a helper method that creates a menu containing every item in every collection. I want to use the collection_item_id to keep track of the currently selected item between requests, but I can't access any attributes of the join model via the Item class.
def helper_method( collection_id )
colls = Collection.find :all
colls.each do |coll|
coll.items.each do |item|
# !!! FAILS HERE ( undefined method `collection_item_id' )
do_something_with( item.collection_item_id )
end
end
end
I tried this as well but it also fails with ( undefined method `collection_item' )
do_something_with( item.collection_item.collection_item_id )
Edit: thanks to serioys sam for pointing out that the above is obviously wrong
I have also tried to access other attributes in the join model, like this:
do_something_with( item.position )
and:
do_something_with( item.collection_item.position )
Edit: thanks to serioys sam for pointing out that the above is obviously wrong
but they also fail.
Can anyone advise me how to proceed with this?
Edit: -------------------->
I found from online documentation that using has_and_belongs_to_many will attach the join table attributes to the retreived items, but apparently it is deprecated. I haven't tried it yet.
Currently I am working on amending my Collection model like this:
class Collection < ActiveRecord::Base
has_many :collection_items, :order => :position, :include => :item
...
end
and changing the helper to use coll.collection_items instead of coll.items
Edit: -------------------->
I've changed my helper to work as above and it works fine - (thankyou sam)
It's made a mess of my code - because of other factors not detailed here - but nothing that an hour or two of re-factoring wont sort out.
In your example you have defined in Item model relationship as has_many for collection_items and collections the generated association method is collection_items and collections respectively both of them returns an array so the way you are trying to access here is wrong. this is primarily case of mant to many relationship. just check this Asscociation Documentation for further reference.
do_something_with( item.collection_item_id )
This fails because item does not have a collection_item_id member.
do_something_with( item.collection_item.collection_item_id )
This fails because item does not have a collection_item member.
Remember that the relation between item and collection_items is a has_many. So item has collection_items, not just a single item. Also, each collection has a list of collection items. What you want to do is probably this:
colls = Collection.find :all
colls.each do |coll|
coll.collection_items.each do |collection_item|
do_something_with( collection_item.id )
end
end
A couple of other pieces of advice:
Have you read the documentation for has_many :through in the Rails Guides? It is pretty good.
You shouldn't need the :source parameters in the has_many declarations, since you have named your models and associations in a sensible way.
I found from online documentation that using has_and_belongs_to_many will attach the join table attributes to the retreived items, but apparently it is deprecated. I haven't tried it yet.
I recommend you stick with has_many :through, because has_and_belongs_to_many is more confusing and doesn't offer any real benefits.
I was able to get this working for one of my models:
class Group < ActiveRecord::Base
has_many :users, :through => :memberships, :source => :user do
def with_join
proxy_target.map do |user|
proxy_owner = proxy_owner()
user.metaclass.send(:define_method, :membership) do
memberships.detect {|_| _.group == proxy_owner}
end
user
end
end
end
end
In your case, something like this should work (haven't tested):
class Collection < ActiveRecord::Base
has_many :collection_items, :order => :position
has_many :items, :through => :collection_items, :source => :item, :order => :position do
def with_join
proxy_target.map do |items|
proxy_owner = proxy_owner()
item.metaclass.send(:define_method, :join) do
collection_items.detect {|_| _.collection == proxy_owner}
end
item
end
end
end
end
Now you should be able to access the CollectionItem from an Item as long as you access your items like this (items.with_join):
def helper_method( collection_id )
colls = Collection.find :all
colls.each do |coll|
coll.items.with_join.each do |item|
do_something_with( item.join.collection_item_id )
end
end
end
Here is a more general solution that you can use to add this behavior to any has_many :through association:
http://github.com/TylerRick/has_many_through_with_join_model
class Collection < ActiveRecord::Base
has_many :collection_items, :order => :position
has_many :items, :through => :collection_items, :source => :item, :order => :position, :extend => WithJoinModel
end
Related
I need to collect objects that are all connected through multiple layers of associations, and I don't know who to do so.
I need to get a collection of CustomText based on a string query param.
Basically I need to do a query that will pull a collection of CustomText by name:
#searched_content = params[:search].downcase
#query = CustomText.where("lower(name) like ?", "%#{#searched_content}%")
but then also filters the #query to only search LineItems that have been a part of an approved order. I am using Spree, where Spree::Order has_many Spree::LineItem. Basically, doing something like this (doesn't work at all, but hopefully you'll be able to see what I'm trying to do):
#query = Spree::LineItem.joins(:order).where(spree_orders: {state: "complete"}).joins(:custom_texts).where("lower(name) like ?", "%#{#searched_content}%"))
Models:
class CustomText < ActiveRecord::Base
belongs_to :custom_set, :inverse_of => :custom_texts
end
class CustomSet < ActiveRecord::Base
belongs_to :spree_line_item, :class_name => Spree::LineItem, :foreign_key => :spree_line_item_id
has_may :custom_texts, :dependent => :destroy, :inverse_of => :custom_set
end
class LineItem < ActiveRecord::Base
has_many :custom_texts, :through => :custom_sets
has_many :custom_sets, :dependent => :destroy, :foreign_key => :spree_line_item_id
end
Any help would be very appreciated.
Well, this was just a simple syntax error with one too many end parenthesis at the end...stupid spelling error.
#query = Spree::LineItem.joins(:order).where(spree_orders: {state: "complete"}).joins(:custom_texts).where("lower(name) like ?", "%#{#searched_content}%")
I'm trying to model items that has_many tags. Items can have multiple tags, but are required to have at least 3 predefined ones.
Here's what I have so far:
class Item < ActiveRecord::Base
has_one :type, :through => :item_tags, :source => :tag
has_one :material, :through => :item_tags, :source => :tag
has_one :use, :through => :item_tags, :source => :tag
has_many :tag, :through => :item_tags
has_many :item_tags
end
This is giving me an ActiveRecord::HasOneThroughCantAssociateThroughCollection when I try to do Item.find(1).type.
I'm not sure how to do this. Can anyone help?
EDIT: I also want to be able to find the three predefined tags by doing item.type and item.use etc.
It's easier to consider this first by seeing how you want your database set up. You want:
Table: Tag
id
tag_name
Table: ItemTag
id
item_id
tag_id
Table: Item
id
type_id
material_id
use_id
So, your model would be more like:
class Item < ActiveRecord::Base
belongs_to :type, :class_name => 'Tag'
belongs_to :material, :class_name => 'Tag'
belongs_to :use, :class_name => 'Tag'
# Require these tags
validates_presence_of :type, :material, :use
has_many :item_tags
has_many :tags, :through => :item_tags
def list_tags
[type, material, use] + tags
end
end
So, your database will have three columns directly in the item table, which link to the tag table. These are required via validations, but you can also set up in your migrations to make these columns not null as well if you wish. The other optional tags keep their same relationship.
You want belongs_to and not has_one, because that pushes the relationship to the Item, where you want it. Has_one puts an item_id column in the Tag table, which is not what you want.
To get the three required tags to appear with the rest of the tags via this method, I'd recommend adding a function just for this use, defined as list_tags above.
Hope that helps!
I think you may want to use custom validations to check that Item.tags includes the ones you require, then use either scopes and class methods to get item.use, item.type, etc. to work as you want.
Item model:
class Item < ActiveRecord::Base
has_many :tags, :class_name => 'ItemTag'
validate :has_type, :has_use, :has_material
# Access methods
def types
self.tags.types
end
def uses
self.tags.uses
end
def materials
self.tags.materials
end
private
# Custom validation methods
def has_type
unless tags.present? and tags.include?(ItemTag.types)
errors.add("Tags must include a type.")
end
end
def has_material
unless tags.present? and tags.include?(ItemTag.materials)
errors.add("Tags must include a material.")
end
end
def has_use
unless tags.present? and tags.include?(ItemTag.use)
errors.add("Tags must include a use.")
end
end
end
ItemTag model:
class ItemTag < ActiveRecord::Base
scope :types, lambda { where(...) }
scope :materials, lambda { where(...) }
scope :uses, lambda { where(...) }
end
You could grab single occurances if preferred using .first in the access methods. You'll need to adjust the where(...) queries based on how you are determining what constitutes a type/material/use.
I have this relation in my Product model:
has_many :features, :class_name => 'ProductFeature', :source => :product_feature, :include => :feature
So I can do Product.features
which works fine. But I want to be able to filter that by fields in the feature table, when and if necessary. For example in pseudo code:
find all product features where feature is comparable
compare is a bool field on the feature.
I have been trying for 2 hours solid and cannot figure it out (without writing a new query completely). I can't figure out how to access the feature table's fields from the Product.features relation, as it seems it can only filter on product_features fields.
This is what I have come up with so far:
def features_compare
features.feature.where(:compare => true)
end
But it just says feature is not a valid method, which I understand.
Edit
I have updated my model so the relationships are clearer:
product.rb:
class Product < ActiveRecord::Base
belongs_to :company
belongs_to :insurance_type
has_many :product_features
has_many :reviews
attr_accessible :description, :name, :company
end
product_feature.rb:
class ProductFeature < ActiveRecord::Base
belongs_to :product
belongs_to :feature
delegate :name, :to => :feature
attr_accessible :value
end
feature.rb
class Feature < ActiveRecord::Base
attr_accessible :name, :compare
end
I want to be able to query the product_features that belong to a product and feature where Feature.compare is true. Something like this:
product.rb
def features_compare
product_features.where(:compare => true)
end
This throws an error because compare in in the Feature model, not ProductFeature. I have tried the following in product_feature.rb:
delegate :compare, :to => :feature
but I didn't help.
I will adding a bounty to this in a few hours so please please help me!
find all product features where feature is comparable is just
ProductFeature.joins(:feature).where(:feature => {:compare => true})
You can make that a bit more reusable by introducing a scope:
#in product_feature.rb
scope :with_feature_like, lambda do |filter|
joins(:feature).where(:feature => filter)
end
#elsewhere
ProductFeature.with_feature_like(:compare => true)
#all the product features of a certain product with at comparable features
some_product.product_features.with_feature_like(:compare => true)
Finally, if you want all products with product features with comparable features, you want something like:
Product.joins(:product_features => :feature).where(:feature => {:compare => true})
which of course you can also turn into a scope on Product.
This seems like a has_many :through relationship. Try changing this:
has_many :features, :class_name => 'ProductFeature', :source => :product_feature, :include => :feature
to this:
has_many :product_features
has_many :features, :through => :product_features
As long as your ProductFeature model has this:
belongs_to :product
belongs_to :feature
And you have the appropriate columns on product_features (product_id, feature_id), then you should be able to access that product's features and all the attributes on both Product and ProductFeature.
See here:
http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association
EDIT: Here's how to filter by feature fields.
Product.joins(:features).where(:features => {:name => "Size"})
#product.each |p| { p.features.where(:comparable => true) } is probably your best bet here, but I'm open to being enlightened.
I need some help with a rails development that I'm working on, using rails 3.
This app was given to me a few months ago just after it's inception and I have since become rather fond of Ruby.
I have a set of Projects that can have resources assigned through a teams table.
A team record has a start date and a end date(i.e. when a resource was assigned and de-assigned from the project).
If a user has been assigned and deassigned from a project and at a later date they are to be assigned back onto the project,
instead of over writting the end date, I want to create a new entry in the Teams table, to be able to keep a track of the dates that a resource was assigned to a certain project.
So my question is, is it possible to have multiple entries in a :has_many through association?
Here's my associations:
class Resource < ActiveRecord::Base
has_many :teams
has_many :projects, :through => :teams
end
class Project < ActiveRecord::Base
has_many :teams
has_many :resources, :through => :teams
end
class Team < ActiveRecord::Base
belongs_to :project
belongs_to :resource
end
I also have the following function in Project.rb:
after_save :update_team_and_job
private
def update_team_and_job
# self.member_ids is the selected resource ids for a project
if self.member_ids.blank?
self.teams.each do |team|
unless team.deassociated
team.deassociated = Week.current.id + 1
team.save
end
end
else
self.teams.each do |team|
#assigning/re-assigning a resource
if self.member_ids.include?(team.resource_id.to_s)
if team.deassociated != nil
team.deassociated = nil
team.save
end
else
#de-assigning a resource
if team.deassociated == nil
team.deassociated = Week.current.id + 1
team.save
end
end
end
y = self.member_ids - self.resource_ids
self.resource_ids = self.resource_ids.concat(y)
self.member_ids = nil
end
end
end
Sure, you can have multiple associations. has_many takes a :uniq option, which you can set to false, and as the documentation notes, it is particularly useful for :through rel'ns.
Your code is finding an existing team and setting deassociated though, rather than adding a new Team (which would be better named TeamMembership I think)
I think you want to just do something like this:
add an assoc for active memberships (but in this one use uniq: => true:
has_many :teams
has_many :resources, :through => :teams, :uniq => false
has_many :active_resources,
:through => :teams,
:class_name => 'Resource',
:conditions => {:deassociated => nil},
:uniq => true
when adding, add to the active_resources if it doesn't exist, and "deassociate" any teams that have been removed:
member_ids.each do |id|
resource = Resource.find(id) #you'll probably want to optimize with an include or pre-fetch
active_resources << resource # let :uniq => true handle uniquing for us
end
teams.each do |team|
team.deassociate! unless member_ids.include?(team.resource.id) # encapsulate whatever the deassociate logic is into a method
end
much less code, and much more idiomatic. Also the code now more explicitly reflects the business modelling
caveat: i did not write a test app for this, code may be missing a detail or two
I am trying to create a model for a ruby on rails project that builds relationships between different words. Think of it as a dictionary where the "Links" between two words shows that they can be used synonymously. My DB looks something like this:
Words
----
id
Links
-----
id
word1_id
word2_id
How do I create a relationship between two words, using the link-table. I've tried to create the model but was not sure how to get the link-table into play:
class Word < ActiveRecord::Base
has_many :synonyms, :class_name => 'Word', :foreign_key => 'word1_id'
end
In general, if your association has suffixes such as 1 and 2, it's not set up properly. Try this for the Word model:
class Word < ActiveRecord::Base
has_many :links, :dependent => :destroy
has_many :synonyms, :through => :links
end
Link model:
class Link < ActiveRecord::Base
belongs_to :word
belongs_to :synonym, :class_name => 'Word'
# Creates the complementary link automatically - this means all synonymous
# relationships are represented in #word.synonyms
def after_save_on_create
if find_complement.nil?
Link.new(:word => synonym, :synonym => word).save
end
end
# Deletes the complementary link automatically.
def after_destroy
if complement = find_complement
complement.destroy
end
end
protected
def find_complement
Link.find(:first, :conditions =>
["word_id = ? and synonym_id = ?", synonym.id, word.id])
end
end
Tables:
Words
----
id
Links
-----
id
word_id
synonym_id
Hmm, this is a tricky one. That is because synonyms can be from either the word1 id or the word2 id or both.
Anyway, when using a Model for the link table, you must use the :through option on the Models that use the Link Table
class Word < ActiveRecord::Base
has_many :links1, :class_name => 'Link', :foreign_key => 'word1_id'
has_many :synonyms1, :through => :links1, :source => :word
has_many :links2, :class_name => 'Link', :foreign_key => 'word2_id'
has_many :synonyms2, :through => :links2, :source => :word
end
That should do it, but now you must check two places to get all the synonyms. I would add a method that joined these, inside class Word.
def synonyms
return synonyms1 || synonyms2
end
||ing the results together will join the arrays and eliminate duplicates between them.
*This code is untested.
Word model:
class Word < ActiveRecord::Base
has_many :links, :dependent => :destroy
has_many :synonyms, :through => :links
def link_to(word)
synonyms << word
word.synonyms << self
end
end
Setting :dependent => :destroy on the has_many :links will remove all the links associated with that word before destroying the word record.
Link Model:
class Link < ActiveRecord::Base
belongs_to :word
belongs_to :synonym, :class_name => "Word"
end
Assuming you're using the latest Rails, you won't have to specify the foreign key for the belongs_to :synonym. If I recall correctly, this was introduced as a standard in Rails 2.
Word table:
name
Link table:
word_id
synonym_id
To link an existing word as a synonym to another word:
word = Word.find_by_name("feline")
word.link_to(Word.find_by_name("cat"))
To create a new word as a synonym to another word:
word = Word.find_by_name("canine")
word.link_to(Word.create(:name => "dog"))
I'd view it from a different angle; since all the words are synonymous, you shouldn't promote any one of them to be the "best". Try something like this:
class Concept < ActiveRecord::Base
has_many :words
end
class Word < ActiveRecord::Base
belongs_to :concept
validates_presence_of :text
validates_uniqueness_of :text, :scope => :concept_id
# A sophisticated association would be better than this.
def synonyms
concept.words - [self]
end
end
Now you can do
word = Word.find_by_text("epiphany")
word.synonyms
Trying to implement Sarah's solution I came across 2 issues:
Firstly, the solution doesn't work when wanting to assign synonyms by doing
word.synonyms << s1 or word.synonyms = [s1,s2]
Also deleting synonyms indirectly doesn't work properly. This is because Rails doesn't trigger the after_save_on_create and after_destroy callbacks when it automatically creates or deletes the Link records. At least not in Rails 2.3.5 where I tried it on.
This can be fixed by using :after_add and :after_remove callbacks in the Word model:
has_many :synonyms, :through => :links,
:after_add => :after_add_synonym,
:after_remove => :after_remove_synonym
Where the callbacks are Sarah's methods, slightly adjusted:
def after_add_synonym synonym
if find_synonym_complement(synonym).nil?
Link.new(:word => synonym, :synonym => self).save
end
end
def after_remove_synonym synonym
if complement = find_synonym_complement(synonym)
complement.destroy
end
end
protected
def find_synonym_complement synonym
Link.find(:first, :conditions => ["word_id = ? and synonym_id = ?", synonym.id, self.id])
end
The second issue of Sarah's solution is that synonyms that other words already have when linked together with a new word are not added to the new word and vice versa.
Here is a small modification that fixes this problem and ensures that all synonyms of a group are always linked to all other synonyms in that group:
def after_add_synonym synonym
for other_synonym in self.synonyms
synonym.synonyms << other_synonym if other_synonym != synonym and !synonym.synonyms.include?(other_synonym)
end
if find_synonym_complement(synonym).nil?
Link.new(:word => synonym, :synonym => self).save
end
end