I am attempting to add in a form field that should allow me to add a record into a join table. The table name contains the ids of the following:
log_id
node_id
So naturally, my models is setup as follows:
class Log
has_and_belongs_to_many :nodes
end
class Node
has_and_belongs_to_many :nodes
end
The objective is that when I create a log, I should be able to associate it with an number of nodes (ergo, servers). And since there is a lot of nodes on hand, it seems to make sense to have a textfield where when you enter a node name, it will pop-up a list of nodes to choose from. However, I am having some difficulty getting that accomplished.
I know how to use the autocomplete plugin, (that had came with Rails), but it seems to only accept a string and not with the id - and apparently not across models. I know how to do an AJAX search (though I am not that familiar with Javascript), but again, getting that ID becomes an issue.
I think that in either case, I may be able to figure how to get that value and put that in - the uncertainty is whether one or the other is the correct approach to getting that value. Which one should I concentrate on? Or is HABTM even appropriate in this?
Related
I am trying to create a Rails app and I have a database consisting of author and a quotation by that author.
Now different users can choose to destroy or kill quotations from the database however it must only be deleted for that particular user i.e other users should still be able to see quotes that they didn't delete even if another user did.
I know that I would need to implement cookies but other than that I am unsure how to proceed. Can anyone point me to a tutorial or give me some pointers to get started on this complex task?
You surely have a User model in your application - one 'Rails-like' way to go about this would be to add a has_and_belongs_to_many relationship between User and Quotation.
This creates a relationship between each individual user and 'their' quotations. This relationship can be deleted without actually deleting a quotation, so all quotations would still be available to other users. If you want each user to be able to see all quotations by default, you would need to set up the relationship in advance.
Assuming you are using Devise to log your users in, all you'd need to do then is to replace Quotation.all with current_user.quotations in whichever controller you are using to display quotations.
The Rails guide linked above is quite helpful but basically you just need to add something like the following:
class User
has_and_belongs_to_many :quotations
before_create :add_quotations
def add_quotations
self.quotations << Quotation.all
end
#etc...
end
class Quotation
has_and_belongs_to_many :users
#etc...
end
and then run a migration adding a new table called users_quotations with the columns user_id and quotation_id.
EDIT
As #Yule pointed out this wouldn't let users see any quotations that were created after they were, and it would be quite annoying to have to set up the join tables in advance, so a more efficient way would be to have an excluded_quotations join table instead. So users can see all quotations except the ones that they have excluded.
Im not sure how to name this question, but Im stucked with kind of an reverse relations in Rails 4. Let me explain it on a real-life example
Order has_many OrderFiles and OrderFile belongs_to Order
My app logic is like this (marketplace like):
User upload some file on the /create_new_order/ page. OrderFile object is saved to the database using form_for OrderFile.new
User searching for the Performer of the Order, apply filters, etc..
User click "Make order" and on certain person. Order object is created
But, how do I link OrderFile to the Order?
It's quite simple when the Order is created first. But when the File is first, how may rails know which order_id link to?
I'm having a trouble with opening AA edit-page for a model, which has a lot of associations.
What I had it's like 50 selects, opening at once. And this page turns to be deadly slow.
After reading this ActiveAdmin: How to handle large associations I considered to use select2 instead of usual select, but things get even worse.
That was because most of the time Rails spent in generating views, not in querying database. So with fancy select2 it reasonably spends even more time in views.
With that knowledge in mind, I decided to not have select inputs on that page at all. So I'll edit "main" object on that slow page, but connected with has_and_belongs_to_many objects should be edited separately.
But after that decision I've faced with a trouble: how should I edit tables with a complex primary key: not just id, but :person_id and :organization_id.
AA by default generates urls like that: /admin/person_organizations/:id/edit, but I need something like this: /admin/person_organizations/:person_id/:organization_id/edit
Any ideas?
ActiveAdmin should be able to handle custom primary keys by default. Just be sure that you add the definition to your model like this:
class Person < ActiveRecord::Base
self.primary_key = 'person_id'
end
After a while I've decided that I don't even need to have multiple keys here since Rails generates artificial id field for habtm tables. And as my goal was to edit this table, I've finished with standard ways of doing this.
Can fields in different but associated tables have the same names is Rails 4 and be distinct. For example, if I have a class Shipping and a class Receiving, where each has the field EnterTrackingNo, and they are associated via a one to one association on the field shipping_id, will there be any issues with this setup / the fields somehow overlap / interfere with one another?
Thanks
There will not be any issue as Rails will automatically add the table name to the SQL queries it builds when it needs to. You'll be able to access the attribute easily as either shipping.EnterTrackingNo, receiving.EnterTrackingNo, shipping.receiving.EnterTrackingNo, receiving.shipping.EnterTrackingNo, etc. and Rails knows which table you're talking about due to the way they're written.
Even when you search for an object, say you want to search for all Shippings with a Receiving item that has EnterTrackingNo == 3 you'd do
Shipping.includes(:receiving).where(receiving: { EnterTrackingNo: 3 })
The only thing to keep in mind is that if you use SQL fragments (writing a where as a String, for example) you MUST write it as table_name.attribute, otherwise you'll get a SQLException: ambiguous column name. For example:
Shipping.includes(:receiving).where("EnterTrackingNo = 3").references(:receivings)
would not work as Rails, and your DB, have no way of knowing WHICH EnterTrackingNo you're talking about. You'd have to write it as:
Shipping.includes(:receiving).where("receivings.EnterTrackingNo = 3").references(:receivings)
So they know you want the Receiving model's attribute.
You'll also notice I add references(:table_name) to the ones with SQL fragments. This is necesary as well since Rails can't tell it needs a join when you just give it a String.
I've come across an oddity in ActiveRecord's #relationship_ids method (that's added automatically when you declare 'has_many'), which saves immediately for existing records, which is causing me some issues, and I wonder if anyone had any useful advice.
I'm running Rails 2.3.5.
Consider this simple scenario, where an article has_many tags, say:
a = Article.first
a.name = "New Name" # No save yet
a.author_id = 1 # No save yet
a.tag_ids = [1,2,3] # These changes are saved to the database
# immediately, even if I don't subsequently
# call 'a.save'
This seems surprising to me. It's specifically causing problems whilst trying to build a preview facility - I want to update a bunch of attributes and then preview the article without saving it - but in this instance the tag changes do get saved, even though no other fields do.
(Of possible relevance is that if 'a' is a new article, rather than an existing one, things behave as I'd expect - nothing is saved until I call 'a.save')
I have a fairly nasty workaround - I can override the tag_ids= method in my model to instead populate an instance variable, and actually save the related models in a before_save callback.
But I'd love to know of a simpler way than me having to do this for every model with a has_many relationship I'd like to create a preview facility for.
Does anyone have any fixes/workarounds/general advice? Thanks!
There's a reason things are this way. It's called foreign keys. In a has many relationship, the information that links to the model that has many is stored outside of that model as a foreign key.
As in Articles, has many tags. The information that links a tag to an article is stored either in the tags table or in a join table. When you call save on an article you're only saving the article.
Active record modifies those other records immediately. Except in the case where you're working with a new article that hasn't been saved yet. Rails will delay creating/updating the associated records if it doesn't know which id to place in the foreign key.
However, if you're modifying existing records, the solution you've decided on is really all that you can do. There's an even uglier hack using accepts_nested_attributes_for, but it's really not worth the effort.
If you're looking to add this behaviour to many models but not all models, you might want to consider writing a simple plugin to redefine the assigment the method you need and add the call back in a single class method call. Have a look at the source of something like acts_as_audited to see how it's done.
If you're looking to add this behaviour to all models, you can probably write a wrapper for has_many to do that.