I'm using of Ruby on Rails.
I have some questions about definition of foreign key.
I defined some models.
When I access book title from class Trade via ISBN like this.
trade = Trade.first
trade.isbn #=> just get isbn in case 1.
trade.isbn.title #=> get book title in case 2.
Why case 2 doesn't work as expected??
class Trade < ActiveRecord::Base
attr_accessible :cost, :isbn, :shop_id, :volume
# belongs_to :book, foreign_key: "isbn" # case 1
belongs_to :isbn, class_name: :Book, foreign_key: :isbn # case 2
belongs_to :shop
end
class Author < ActiveRecord::Base
attr_accessible :age, :name
has_many :books
has_many :trades, through
end
class Book < ActiveRecord::Base
self.primary_key = :isbn
attr_accessible :author_id, :cost, :isbn, :publish_date, :title
belongs_to :author
end
class Shop < ActiveRecord::Base
attr_accessible :name
has_many :trades
end
I am not entirely sure what you're asking, what behavior you're seeing, or what behavior you expected. That said, this is what's happening with the code you've pasted (case 2?):
trade = Trade.first
trade.isbn
This returns the Book instance referenced by Trade#isbn.
trade.isbn.title
This is equivalent to
book = trade.isbn
book.title
which returns the title of the Book instance referenced by Trades#isbn. Is this not what you expected?
So Your question is what is difference between symbol (:isbn) and string ("isbn")?
In shot symbols are considered Rubys immutable strings You can read more here:
http://www.robertsosinski.com/2009/01/11/the-difference-between-ruby-symbols-and-strings/
In general convention is to use symbols as keys inside You options hashes that You pass to methods, though some libs/gems etc support both. But in particular case of Yours it looks like that this value is being typecasted to string, so everything that is passed as option to foreign_key will converted to string using to_s.
Related
I want to know what I'm doing wrong as my Categories "name" that I specify on rails console are not uploading directly to my postgresql database.
My first Model (category.rb)file
class Category < ApplicationRecord
attr_accessible :name
has_many :content
end
My Second Model (content.rb)file
class Content < ApplicationRecord
attr_accessible :title, :body, :category_id, :author_id
belongs_to :category
end
I've added two categories inside this model
"Football" and Cricket using the code below:
category = Category.create(:name => "Football")
category = Category.create(:name => "Cricket")
The above code creates category id and tables in the postgresql not the name I specified.
Please help.. Please reply if you need anything else
class Category < ApplicationRecord
attr_accessible :name
# has_many :content -- This is wrong
has_many :contents # This is how it should be
end
Also has hashrocket suggested try running migration.
What is the result of running the following in console?
c = Category.new
c.name = "football"
c.save
If this gives you an error then going through the error message will show what is wrong.
As I am learning RoR now, I would like to know a more appropriated (rails) way to achieve that the application only shows associated resources.
Right now I have the following models:
class Account < ActiveRecord::Base
has_many :billing_accounts
has_many :addresses
end
class BillingAccount < ActiveRecord::Base
belongs_to :invoice_address,
class_name: "Address",
foreign_key:"invoice_address_id"
end
class Address < ActiveRecord::Base
has_many :billing_accounts
belongs_to :account
end
In my edit.billing_account I have this form:
= simple_form_for([:account, #billing_account]) do |f|
= f.association :invoice_address
I expected that only the associated address will be shwon, but this shows "all" address records in the database (also from other user accounts).
Users only should be able to see account.addresses and for now I do this with:
= f.association :invoice_address, collection: current_user.account.addresses.all
But I am sure there is better way to do this inside the models. For every form I now use current_user.account.MODEL.all but that is not very DRY I think.
So basically what I want is only to use =f.association :invoice_address and BillingAccount should know it only can show the account.addresses.
Suggestions are welcome. Thanks!
You just need to set default_scope for nested models:
class Address < ActiveRecord::Base
default_scope { where(account_id: current_user.account_id) }
But in this case you should define current_user in models
In your case you should use f.simple_fields_for instead of f.association as described here: https://github.com/plataformatec/simple_form/wiki/Nested-Models
class BillingAccount < ActiveRecord::Base
belongs_to :invoice_address,
class_name: "Address",
foreign_key:"invoice_address_id"
accepts_nested_attributes_for :invoice_address
end
View:
= simple_form_for([:account, #billing_account]) do |f|
= f.simple_fields_for :invoice_address do |f_address|
= f_address.input :street
= f_address.input :zipcode
...
Don't forget to build invoice_address of account in a controller if it is needed. For example:
class BillingAccountController < ApplicationController
def new
#billing_account = BillingAccount.new
#billing_account.build_invoice_address
end
Since you're using has_many you can use the plural version of the model name rather than current_user.account.MODEL.all.
Like this:
current_user.account.addresses
or
current_user.account.billing_accounts
It even works the other way with belongs_to:
#address = Address.last
#address.accounts
Try to add conditions to belongs_to association:
class BillingAccount < ActiveRecord::Base
belongs_to :invoice_address,
->(billing_account) { where "account_id = #{billing_account.account_id}" },
class_name: "Address",
foreign_key:"invoice_address_id"
end
I have a model called Course which needs to be associated with exams and assignments. I want to able to write code like this:
>>c = Course.new
>>assignment1 = c.assignments << Assignment.new
>>exam1 = c.exams << Exam.new
c.assessments should now include both exam1 and assignment1
How I think this should be accomplished (using single table inheritance from the Assessment model):
class Course < ActiveRecord::Base
has_many :assessments
attr_accessible :title, :name, :startDate, :endDate, :color
end
class Assessment < ActiveRecord::Base
belongs_to :course
attr_accessible :end_at, :name, :start_at, :type, :weight
end
class Assignment < Assessment
end
class Exam < Assessment
end
I've tried my best to find out how to do this but i cant seem to figure it out. Any help would be appreciated.
Course has only assesments associations so you should be able to write code like this:
c = Course.new
c.assesments << Assignment.new
c.assesments << Exam.new
Also make sure that assesments table has type column with datatype string.
I need to link Comments to a Post. However the Comment could be (user generated) a simple text, (system generated) a link or an (system generated) image.
At first they all shared the same attributes. So I just needed to create a category attribute, and do different stuff with the text attribute based on that category.
example:
class Comment < ActiveRecord::Base
belongs_to :post
belongs_to :author, :class_name => "User"
CATEGORY_POST = "post"
CATEGORY_IMAGE = "image"
CATEGORY_LINK = "link"
validates :text, :author, :category, :post, :presence => true
validates_inclusion_of :category, :in => [CATEGORY_POST, CATEGORY_IMAGE, CATEGORY_LINK]
attr_accessible :author, :text, :category, :post
def is_post?
self.category == CATEGORY_POST
end
def is_link?
self.category == CATEGORY_LINK
end
def is_image?
self.category == CATEGORY_IMAGE
end
end
However this wil not suffice now, because I doesn't feel clean to dump every value in a generic "text" property. So I was thinking about create a polymorphic model (and if needed in a factory pattern). But when I googled about polymorphic models, I get examples like a Comment on a Post, but the same Comment on a Page, kind of relations. Is my understanding of polymorphic different (a model that acts different in different situations, compared to a model that acts the same under different scopes)?
So how would I set up this kind of relationship?
I was thinking of (and please correct me)
Post
id
Comment
id
post_id
category (a enum/string or integer)
type_id (references either PostComment, LinkComment or ImageComment based on category)
author_id
PostComment
id
text
LinkComment
id
link
ImageComment
id
path
User (aka Author)
id
name
But I have no clue how to setup the model so that I can call post.comments (or author.comments) to get all comments. A nice to have would be that the creation of a comment would be through comment and not link/image/postcomment (comment acting as the factory)
My main question is, how to setup up the activerecord models, so the relations stay intact (a author has comments and a post has comments. Comments being either a Link, Image or Postcomment)
I'm going to answer only your main question, the model setup. Given the columns and tables you used in your question, with the exception of Comment, you can use the following setup.
# comment.rb
# change category to category_type
# change type_id to category_id
class Comment < ActiveRecord::Base
belongs_to :category, polymorphic: true
belongs_to :post
belongs_to :author, class_name: 'User'
end
class PostComment < ActiveRecord::Base
has_one :comment, as: :category
end
class LinkComment < ActiveRecord::Base
has_one :comment, as: :category
end
class ImageComment < ActiveRecord::Base
has_one :comment, as: :category
end
with that setup, you can do the following.
>> post = Post.first
>> comments = post.comments
>> comments.each do |comment|
case comment.category_type
when 'ImageComment'
puts comment.category.path
when 'LinkComment'
puts comment.category.link
when 'PostComment'
puts comment.category.text
end
end
Let's say you have the following models:
class User < ActiveRecord::Base
has_many :comments, :as => :author
end
class Comment < ActiveRecord::Base
belongs_to :user
end
Let's say User has an attribute name, is there any way in Ruby/Rails to access it using the table name and column, similar to what you enter in a select or where query?
Something like:
Comment.includes(:author).first.send("users.name")
# or
Comment.first.send("comments.id")
Edit: What I'm trying to achieve is accessing a model object's attribute using a string. For simple cases I can just use object.send attribute_name but this does not work when accessing "nested" attributes such as Comment.author.name.
Basically I want to retrieve model attributes using the sql-like syntax used by ActiveRecord in the where() and select() methods, so for example:
c = Comment.first
c.select("users.name") # should return the same as c.author.name
Edit 2: Even more precisely, I want to solve the following problem:
obj = ANY_MODEL_OBJECT_HERE
# Extract the given columns from the object
columns = ["comments.id", "users.name"]
I don't really understand what you are trying to achieve. I see that you are using polymorphic associations, do you need to access comment.user.name while having has_many :comments, :as => :author in your User model?
For you polymorphic association, you should have
class Comment < ActiveRecord::Base
belongs_to :author, :polymorphic => true
end
And if you want to access comment.user.name, you can also have
class Comment < ActiveRecord::Base
belongs_to :author, :polymorphic => true
belongs_to :user
end
class User < ActiveRecord::Base
has_many :comments, :as => :author
has_many :comments
end
Please be more specific about your goal.
I think you're looking for a way to access the user from a comment.
Let #comment be the first comment:
#comment = Comment.first
To access the author, you just have to type #comment.user and If you need the name of that user you would do #comment.user.name. It's just OOP.
If you need the id of that comment, you would do #comment.id
Because user and id are just methods, you can call them like that:
comments.send('user').send('id')
Or, you can build your query anyway you like:
Comment.includes(:users).where("#{User::columns[1]} = ?", #some_name)
But it seems like you're not doing thinks really Rails Way. I guess you have your reasons.