tl;dr: Is it possible to intercept posted values from a nested model for further processing? I've tried everything I can think of to access the nested attributes to use for a before_save callback, but that may be only a testament to the limits of my imagination.
I'm writing a library application, where books can have many authors and vice versa. That bit is working just fine with a has_many_through and accepts_nested_attributes_for. The app saves all the book and author information just fine. Except... I can't seem to write a working before_save on either the Author or Book model to check if the Author that we're trying to create exists. Here's what I already have:
class Book < ActiveRecord::Base
has_many :authorships
has_many :authors, :through => :authorships
accepts_nested_attributes_for :authors, :authorships
end
class Author < ActiveRecord::Base
has_many :authorships
has_many :books, :through => :authorships
before_save :determine_distinct_author
def determine_distinct_author
Author.find_or_create_by_author_last( #author )
end
end
## books_controller.rb ##
def new
#book = Book.new
#book.authors.build
respond_to do |format|
format.html
format.xml { render :xml => #book }
end
end
def create
#book = Book.new(params[:book])
#author = #book.authors #I know this line is wrong. This is the problem (I think.)
# more here, obviously, but nothing out of ordinary
end
When I post the form, the dev log passes on this:
Parameters: {"commit"=>"Create Book",\
"authenticity_token"=>"/K4/xATm7eGq/fOmrQHKyYQSKxL9zlVM8aqZrSbLNC4=",\
"utf8"=>"✓", "book"{"title"=>"Test", "ISBN"=>"", "genre_id"=>"1", "notes"=>"", \
"authors_attributes"=>{"0"{"author_last"=>"McKinney", "author_first"=>"Jack"}}, \
"publisher"=>"", "pages"=>"", "language_id"=>"1", "location_id"=>"1"}}
So... the data's there. But how do I get to it to process it? When I post the data, here's that log:
Author Load (0.4ms) SELECT `authors`.* FROM `authors` WHERE\
`authors`.`author_last` IS NULL LIMIT 1
I've done a fair bit of searching around to see what there is out there on nested attributes, and I see a lot on the form side, but not much on how to get to the assets once they're submitted.
Any explanation of why the solution which works does actually work would also be appreciated. Thanks.
First, this line
#author = #book.authors
assigns an array of authors to #author, but in your before_save you seem to be expecting a single author model. Secondly, the #author variable is scoped to the controller and will be empty in your model's scope.
Remove that line and try this in your Book class (not tested):
def determine_distinct_author
authors.each do |author|
Author.find_or_create_by_author_last( author )
end
end
1) The nested attributes is an array, and should be accessed as an array. Getting the submission from the one model to the next still presents quite a problem.
2) accepts_nested_attributes_for is probably not going to help out a whole lot, and there will undoubtedly be a lot of custom processing which will have to happen between now and when the whole system is fully functional. Probably best to ditch it now and move on.
In that direction: It looks like Ryan Bates has done a recent bit on the jQuery TokenInput plugin which will take care of a lot of the autocomplete feature on the author. More to the larger problem (and a bit harder to find), is a follow up that he posted to some issues with the plugin on working with new entries.
I am not quite sure what you are trying to accomplish, but inside your Author you have a before_save callback, and that is obviously giving the error.
To me it seems you are looking for an author with the given name, and then want to use that? Is that correct?
Using a nested form, you will always create a new author, unless you want to use something like a select-box, and then select an author-id (which is part of the book, so not nested), instead of the authors details.
UX-wise, i would offer the option to either select an existing author (use an autocomplete field), or create a new one (using the nested fields option --without your before_save callback).
Related
I have multiple models that in practice are created and deleted together.
Basically I have an Article model and an Authorship model. Authorships link the many to many relation between Users and Articles. When an Article is created, the corresponding Authorships are also created. Right now, this is being achieved by POSTing multiple times.
However, say only part of my request works. For instance, I'm on bad wifi and only the create article request makes it through. Then my data is in a malformed half created, half not state.
To solve this, I want to send all the data at once, then have Rails split up the data into the corresponding controllers. I've thought of a couple ways to do this. The first way is having controllers handle each request in turn, sort of chaining them together. This would require the controllers to call the next one in the chain. However, this seems sorta rigid because if I decide to compose the controllers in a different way, I'll have to actually modify the controller code itself.
The second way splits up the data first, then calls the controller actions with each bit of data. This way seems more clean to me, but it requires some logic either in the routing or in a layer independent of the controllers. I'm not really clear where this logic should go (another controller? Router? Middleware?)
Has anybody had experience with either method? Is there an even better way?
Thanks,
Nicholas
Typically you want to do stuff like this -- creating associated records on object creation -- all in the same transaction. I would definitely not consider breaking up the creation of an Authorship and Article if creating an Authorship is automatic on Article creation. You want a single request that takes in all needed parameters to create an Article and its associated Authorship, then you create both in the same transaction. One way would be to do something like this in the controller:
class Authorship
belongs_to :user
belongs_to :article
end
class Article
has_many :authorships
has_many :users, through: :authorships
end
class ArticlesController
def create
#article = Article.new({title: params[:title], stuff: [:stuff]...})
#article.authorships.build(article: #article, user_id: params[:user_id])
if #article.save
then do stuff...
end
end
end
This way when you hit #article.save, the processing of both the Article and the Authorship are part of the same transaction. So if something fails anywhere, then the whole thing fails, and you don't end up with stray/disparate/inconsistent data.
If you want to assign multiple authorships on the endpoint (i.e. you take in multiple user id params) then the last bit could become something like:
class ArticlesController
def create
#article = Article.new({title: params[:title], stuff: [:stuff]...})
params[:user_ids].each do |id|
#article.authorships.build(article: #article, user_id: id)
end
if #article.save
then do stuff...
end
end
end
You can also offload this kind of associated object creation into the model via a virtual attribute and a before_save or before_create callback, which would also be transactional. But the above idiom seems more typical.
I would handle this in the model with one request. If you have a has_many relationship between Article and Author, you may be able to use accept_nested_attributes_for on your Article model. Then you can pass Authorship attributes along with your Article attributes in one request.
I have not seen your code, but you can do something like this:
model/article.rb
class Article < ActiveRecord::Base
has_many :authors, through: :authorship # you may also need a class_name: param
accepts_nested_attributes_for: :authors
end
You can then pass Author attributes to the Article model and Rails will create/update the Authors as required.
Here is a good blog post on accepts_nested_attributes_for. You can read about it in the official Rails documentation.
I would recommend taking advantage of nested attributes and the association methods Rails gives you to handle of this with one web request inside one controller action.
I've been looking, and can't find a good answer for how to delete records in a HABTM table. I assume a lot of people have this same requirement.
Simply, I have Students, Classes, and Classes_Students
I want a student to be able to drop a class, or delete the HABTM record that has signed that student up for that class.
There must be a simple answer to this. Does anyone know what it is?
The reason why .destroy or .delete does not work on this situation is due to the missing primary key in the middle table. However, our parent objects have this really cool method called {other_obj}_ids. It is a collection of ids on the left table object, of the right table object. This information is of course populated from our middle table.
So with that in mind, we have 2 object classes (Student, and Classes). Active record magic can generally figure out the middle table if you are not doing anything fancy, but it is recommended to use has_many :through.
class Student < ActiveRecord::Base
has_and_belongs_to_many :classes
end
class Classes < ActiveRecord::Base
has_and_belongs_to_many :students
end
What we can now do in terms of the middle table with this setup...
student = Student.find_by(1)
student.classes # List of class objects this student currently has.
student.class_ids # array of class object ids this student currently has
# how to remove a course from the middle table pragmatically
course = Course.find_by({:name => 'Math 101'})
# if this is actually a real course...
unless course.nil?
# check to see if the student actually has the course...
if student.class_ids.include?(course.id)
# update the list of ids in the array. This triggers a database update
student.class_ids = student.class_ids - [course.id]
end
end
I know this is a little late to answer this, but I just went through this exact situation tonight and wanted to share the solution here.
Now, if you want this deleted by the form, since you can now see how it is handled pragmatically, simply make sure the form input is nested such that it has something to the effect of:
What kind of trouble are you having? Do you have the appropriate :dependent=>:destroy and :inverse_of=>[foo] on your relations?
Let's say a class had a course title. You can do:
student.classes.find_by_course_title("Science").delete
So the proper answer here is to do something like this in your view:
<%= link_to 'Remove', cycle_cycles_group_path(#cycle, cycle), method: :delete %><br />
cycle is from a block the above code is within.
#cycle is an instance variable from the join models controller.
cycle_cycles_group_path is the nested join table "cycles_groups" under the model "Cycle" in the routes.rb file:
resources :cycles do
resources :cycles_groups do
end
end
and the join model controller looks like this:
def destroy
#cycles_group = CyclesGroup.find(params[:id])
#cycle = #cycles_group.cycle
#cycles_group.destroy
puts "cycle: #{#cycle}"
respond_to do |format|
format.html {redirect_to cycle_path(#cycle), notice: 'Training Week was successfully removed!'}
end
end
I've got an ActiveAdmin index page
ActiveAdmin.register Bill
And I am trying to display links to associated models
index do
column "User" do |bill|
link_to bill.user.name, admin_user_path(bill.user)
end
end
But I run into the N+1 query problem - there's a query to fetch each user.
Is there a way of eager loading the bills' users?
The way to do this is to override the scoped_collection method (as noted in Jeff Ancel's answer) but call super to retain the existing scope. This way you retain any pagination/filtering which has been applied by ActiveAdmin, rather than starting from scratch.
ActiveAdmin.register Bill do
controller do
def scoped_collection
super.includes :user
end
end
index do
column "User" do |bill|
link_to bill.user.name, admin_user_path(bill.user)
end
end
end
As noted in official documentation at http://activeadmin.info/docs/2-resource-customization.html
There is an answer on a different post, but it describes well what you need to do here.
controller do
def scoped_collection
Bill.includes(:user)
end
end
Here, you will need to make sure you follow scope. So if your controller is scope_to'ed, then you will want to replace the model name above with the scope_to'ed param.
The existing answers were right at the time, but ActiveAdmin supports eager loading with a much more convenient syntax now:
ActiveAdmin.register Bill do
includes :user
end
See the docs for resource customization
IMPORTANT EDIT NOTE : what follows is actually false, see the comments for an explanation. However I leave this answer where it stands because it seems I'm not the only one to get confused by the guides, so maybe someone else will find it useful.
i assume that
class Bill < ActiveRecord::Base
belongs_to :user
end
so according to RoR guides it is already eager-loaded :
There’s no need to use :include for immediate associations – that is,
if you have Order belongs_to :customer, then the customer is
eager-loaded automatically when it’s needed.
you should check your SQL log if it's true (didn't know that myself, i was just verifying something about :include to answer you when i saw this... let me know)
I've found scoped_collection loads all the entries, instead of just the ones for the page you are displaying. I think a better option is apply_collection_decorator that will only preload the items you are effectively displaying.
controller do
def apply_collection_decorator(collection)
collection.includes(:user)
end
end
Taking this article as a starting point:
Rails Way Blog - Association Proxies
and looking specifically at
def create
#todo_list = current_user.todo_lists.build params[:todo_list]
if #todo_list.save
redirect_to todo_list_url(#todo_list)
else
render :action=>'new'
end
end
This is a way of making sure you assign ownership to the user
BUT supposing the ToDo list was a many-many relationship associated in a has_many through i.e.
def User < AR:Base
has_many :user_todos
has_many :todo_lists, :through => :user_todos
end
At this point...
#todo_list = current_user.todo_lists.build params[:todo_list]
still works but only the todo_list is saved and not the join. How can I get the joy of association proxies without having lots of nested if/else should the join or Todo instance not validate when saved.
I was thinking of something along the lines of...
#todo_list = cu.user_todos.build.build_to_do(params[:todo_list])
but as I mentioned above the user_todos don't get saved.
Your help is greatly appreciated!
Kevin.
Try doing something along the lines of:
current_user.todo_lists << TodoList.new(params[:todo_list])
I got it working...
At first I had:
#todo_list = #user.todo_lists.build params[:todo_list]
#todo_list.save!
This works when TodoList simply belongs_to User but not when it's a many-to-many relationship. When I changed the relationship I had to do...
#todo_list = #user.todo_lists.build params[:todo_list]
#user.save!
This saved the #user, the join and the #todo_list.
Obvious I suppose but then I wonder if the original example should also
current_user.save!
instead of
#todo_list.save!
I thought the idea behind build was that it validates and saves the associations when you save the parent so does the example at Rails Way miss the point? or more likely am I?
First, I feel like I am approaching this the wrong way, but I'm not sure how else to do it. It's somewhat difficult to explain as well, so please bear with me.
I am using Javascript to allow users to add multiple text areas in the edit form, but these text areas are for a separate model. It basically allows the user to edit the information in two models rather than one. Here are the relationships:
class Incident < ActiveRecord::Base
has_many :incident_notes
belongs_to :user
end
class IncidentNote < ActiveRecord::Base
belongs_to :incident
belongs_to :user
end
class User < ActiveRecord::Base
has_many :incidents
has_many :incident_notes
end
When the user adds an "incident note", it should automatically identify the note with that particular user. I also want multiple users to be able to add notes to the same incident.
The problem I ran into is that when a user adds a new text area, rails isn't able to figure out that the new incident_note belongs_to the user. So it ends up creating the incident_note, but the user_id is nil. For example, in the logs I see the following insert statement when I edit the form and add a new note:
INSERT INTO "incident_notes" ("created_at", "updated_at", "user_id", "note", "incident_id") VALUES('2010-07-02 14:09:11', '2010-07-02 14:09:11', NULL, 'Another note', 8)
So what I've decided to try to do is manipulate the params for :incident in the update method. This way I can just add the user_id myself, however this seems un-rails-like, but I'm not sure how else to it.
When the form is submitted, the parameters look like this:
Parameters: {"commit"=>"Update", "action"=>"update", "_method"=>"put", "authenticity_token"=>"at/FBNxjq16Vrk8/iIscWn2IIdY1jtivzEQzSOn0I4k=", "id"=>"18", "customer_id"=>"4", "controller"=>"incidents", "incident"=>{"title"=>"agggh", "incident_status_id"=>"1", "incident_notes_attributes"=>{"1279033253229"=>{"_destroy"=>"", "note"=>"test"}, "0"=>{"id"=>"31", "_destroy"=>"", "note"=>"asdf"}}, "user_id"=>"2", "capc_id"=>"SDF01-071310-004"}}
So I thought I could edit this section:
"incident_notes_attributes"=>{"1279033253229"=>{"_destroy"=>"", "note"=>"test"}, "0"=>{"id"=>"31", "_destroy"=>"", "note"=>"another test"}}
As you can see, one of them does not have an id yet, which means it will be newly inserted into the table.
I want to add another attribute to the new item so it looks like this:
"incident_notes_attributes"=>{"1279033253229"=>{"_destroy"=>"", "note"=>"test", "user_id" => "2"}, "0"=>{"id"=>"31", "_destroy"=>"", "note"=>"another test"}}
But again this seems un-rails-like and I'm not sure how to get around it. Here is the update method for the Incident controller.
# PUT /incidents/1
# PUT /incidents/1.xml
def update
#incident = #customer.incidents.find(params[:id])
respond_to do |format|
if #incident.update_attributes(params[:incident])
# etc, etc
end
I thought I might be able to add something like the following:
params[:incident].incident_note_attributes.each do |inote_atts|
for att in inote_atts
if att.id == nil
att.user_id = current_user.id
end
end
end
But obviously incident_note_attributes is not a method. So I'm not sure what to do. How can I solve this problem?
Sorry for the wall of text. Any help is much appreciated!
I have a similar requirement and this is how I tackled it:
class Incident < ActiveRecord::Base
has_many :incident_notes
belongs_to :user
attr_accessor :new_incident_note
before_save :append_incident_note
protected
def append_incident_note
self.incident_notes.build(:note => self.new_incident_note) if !self.new_incident_note.blank?
end
end
and then in the form, you just use a standard rails form_for and use the new_incident_note as the attribute.
I chose this method because I knew it was just throwing data into the notes with minor data validations. If you have in depth validations, then I recommend using accepts_nested_attributes_for and fields_for. That is very well documented here.