When creating a record I want to set a column called original_id to the value of its primary key (in this case id). In essence, the rows will become hierarchal and they will look like this:
| id | original_id |
| -- | ----------- |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| .. | 1 |
| 42 | 42 |
| 43 | 42 |
The model will look like this:
class AccountTransaction < ApplicationRecord
belongs_to :original,
class_name: 'AccountTransaction',
foreign_key: :original_id
end
It's easy to create the record then update like this:
record = AccountTransaction.create
record.update(original: record)
But I am looking for a more elegant solution, one that doesn't require two database transactions. Thanks for your help.
You could do something with an after_create callback.
class AccountTransaction < ApplicationRecord
after_create :upate_original_id
def update_original_id
update_attribute(original_id: id)
end
end
i am new to ROR.
i am building a classified ads app, i have the following tables in my database:
(some fields have been removed for simplicity)
Table Uers
This table stores all the users.
user_id
name
email
password
Table Ads
This table stores all the ads.
ad_id
users_user_id (FK)
title
desc
cat_id (FK)
created_at
Sample data:
------------------------------------------------------------------------------
| ad_id | users_user_id | title | desc | cat_id | created_at |
------------------------------------------------------------------------------
| 1 | 1 | iphone 4 | brand new | 2 | 30-11-2015 |
------------------------------------------------------------------------------
Table categories
This table stores all the available categories. cat_id in the ads table relates to cat_id in this table.
cat_id
category
parent_cid
Sample data:
-------------------------------------------
|cat_id| category | parent_cid |
-------------------------------------------
|1 | Electronics | NULL |
|2 | Mobile Phone | 1 |
|3 | Apartments | NULL |
|4 | Apartments - Sale | 3 |
-------------------------------------------
Table ads_attribute
This table contains all the available attributes for a particular category. Relates to categories table.
attr_id
cat_id (FK)
attr_label
attr_name
Sample data:
-----------------------------------------------------------
|attr_id | cat_id | attr_label | attr_name |
-----------------------------------------------------------
|1 | 2 | Operating System | Operating_System |
|2 | 2 | Is Touch Screen | Touch_Screen |
|3 | 2 | Manufacturer | Manufacturer |
|4 | 3 | Bedrooms | Bedrooms |
|5 | 3 | Total Area | Area |
|6 | 3 | Posted By | Posted_By |
-----------------------------------------------------------
Table ads_attr_value
This table stores the attribute value for each ad in ads table.
attr_val_id
attr_id (FK)
ad_id
attr_val
Sample data:
---------------------------------------------
|attr_val_id | attr_id | ad_id | attr_val |
---------------------------------------------
|1 | 1 | 1 | Ios 8 |
|2 | 2 | 1 | 1 |
|3 | 3 | 1 | Apple |
---------------------------------------------
What is the best way (the rails way) to validate the data before storing it in the the ads_attr_value table, given the fact that the values would be in select fields and the user can change them easily for example from Ios 8 to "blabla".
I've thought of storing all the possible values for each attribute in a new table and then check if a value sent by the user exist in that table before storing it in the ads_attr_value. what do you think? I am sure that there is a better way.thanks for sharing.
The rails way would probably to define your relationships with ActiveRecord associations : http://guides.rubyonrails.org/association_basics.html.
Therefore you could easily define on your model
class AdsAttrVal < ActiveRecord::Base
belongs_to :ad
validates :ad, presence: true
end
However please keep in mind that rails way to store an id of the table is to name it "id" and not "model_id" like you did ("user_id", "id"). My exemple suppose that the rails way is respected...
You have to specify the validations you want inside <yourModel>.rb (the model file) . For exame if you want to validate if ad_id is a number you should add the numericality parameter in the validates statement, see below:
class AdsAttrValue < ActiveRecord::Base
validates :ad_id, numericality: true
#validate if add_att_value has the permitted values
validate :myCustomValidation
def myCustomValidation
#your logic of validation goes here
#you can access here all the fields from this object recently created
if attr_val == something
#do something
end
end
end
See that validations from rails have an s at the end (validates), and your own written validations do not have (validate).
This validations are executed when creating the object before storing in database in order to see if it complies the validations and not stored it it does not comply. You can add errors in your own validation to let the user know what gone wrong. Go further with this reading of validations in ruby on rails
I have 2 tables for example:
user_places
----------------
| id | place_id|
----------------
| 1 | 1 |
----------------
| 1 | 5 |
----------------
| 1 | 6 |
----------------
| 2 | 8 |
And a places table
--------------------------------------------
| id | title | description | image_url |
--------------------------------------------
| 1 | 1 | description1 | image1 |
--------------------------------------------
| 2 | 5 | description2 | image2 |
--------------------------------------------
| 3 | 6 | description3 | image3 |
--------------------------------------------
| ...| ... | description4 | image4 |
How to make the association in both models so I can get all places of user_places's id = 1 in rails console?
You'll want to look up foreign_keys, especially pertaining to Rails.
Rails is basically a way for you to interact with a relational database. As such, if you know how to correctly structure a relational DB, you'll be able to better understand Rails' ActiveRecord associations, and how they fit into applications.
--
How to make the association in both models so I can get all places of user_places's id = 1
You'd do this:
#app/models/user.rb
class User < ActiveRecord::Base
has_and_belongs_to_many :places
end
#app/models/places.rb
class Place < ActiveRecord::Base
has_and_belongs_to_many :users
end
This means you have to change your user_places table to the following:
#places_users
#user_id | place_id
This will allow you to call:
$ #user = User.find "1"
$ #user.places #-> 1,5,6
--
The other answer recommended a has_many :through relationship. Whilst this allows you to add other data into your join model, it means you have to include a user_places model for no real reason (at this stage).
I would recommend using has_and_belongs_to_many for the moment. This limits you to only having references in your join table, but makes the entire association much simpler:
The big caveat here is that you'll need to change your user_places table to have an alphabetical nameflow (places_users), and make sure you only have the two foreign_keys as columns: user_id | place_id
I don't understand how to get the columns I want from rails. I have two models - A User and a Profile. A User :has_many Profile (because users can revert back to an earlier version of their profile):
> DESCRIBE users;
+----------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| username | varchar(255) | NO | UNI | NULL | |
| password | varchar(255) | NO | | NULL | |
| last_login | datetime | YES | | NULL | |
+----------------+--------------+------+-----+---------+----------------+
> DESCRIBE profiles;
+----------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| user_id | int(11) | NO | MUL | NULL | |
| first_name | varchar(255) | NO | | NULL | |
| last_name | varchar(255) | NO | | NULL | |
| . . . . . . |
| . . . . . . |
| . . . . . . |
+----------------+--------------+------+-----+---------+----------------+
In SQL, I can run the query:
> SELECT * FROM profiles JOIN users ON profiles.user_id = users.id LIMIT 1;
+----+-----------+----------+---------------------+---------+---------------+-----+
| id | username | password | last_login | user_id | first_name | ... |
+----+-----------+----------+---------------------+---------+---------------+-----+
| 1 | john | ****** | 2010-12-30 18:04:28 | 1 | John | ... |
+----+-----------+----------+---------------------+---------+---------------+-----+
See how I get all the columns for BOTH tables JOINED together? However, when I run this same query in Rails, I don't get all the columns I want - I only get those from Profile:
# in rails console
>> p = Profile.joins(:user).limit(1)
>> [#<Profile ...>]
>> p.first_name
>> NoMethodError: undefined method `first_name' for #<ActiveRecord::Relation:0x102b521d0> from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.1/lib/active_record/relation.rb:373:in `method_missing' from (irb):8
# I do NOT want to do this (AKA I do NOT want to use "includes")
>> p.user
>> NoMethodError: undefined method `user' for #<ActiveRecord::Relation:0x102b521d0> from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.1/lib/active_record/relation.rb:373:in method_missing' from (irb):9
I want to (efficiently) return an object that has all the properties of Profile and User together. I don't want to :include the user because it doesn't make sense. The user should always be part of the most recent profile as if they were fields within the Profile model. How do I accomplish this?
I think the problem has something to do with the fact that the Profile model doesn't have attributes for User...
Use select() to name the columns you want. At least this works in Rails 3.0.9.
Background: my application has a primary table named :rights. I wanted to be able to ascribe a tag and color to a given :right record so I could easily pick it out of an index listing. This doesn't cleanly fit the Rails picture of associated records; most :rights will never be tagged, and the tags are completely arbitrary (user input via tag/edit).
I could try duplicating the tag data in the :right record, but that violates normal form. Or I could try querying :tags for each :right record, but that is a painfully inefficient approach. I want to be able to join the tables.
MySQL console shows:
mysql> describe rights;
+------------+---------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+---------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
...
| Tagid | int(11) | YES | | NULL | |
+------------+---------------+------+-----+---------+----------------+
mysql> describe tags;
+------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| TagName | varchar(255) | YES | | NULL | |
| TagColor | varchar(255) | YES | | NULL | |
| created_at | datetime | YES | | NULL | |
| updated_at | datetime | YES | | NULL | |
+------------+--------------+------+-----+---------+----------------+
I am going to use TagName and TagColor in views/rights/index.html.erb, so I want the rights controller to include those columns in the #rights object it passes to the view. Since not every :right has a :tag, I want to use an outer join:
#rights = Right.joins("LEFT OUTER JOIN tags ON rights.Tagid = tags.id")
But, as everyone has found, this alone doesn't work: a block reference to TagName produces a server error. However, if I add a select at the end, all is well:
#rights = Right.joins("LEFT OUTER JOIN tags ON rights.Tagid = tags.id").select("rights.*,tags.TagName as TagName,tags.TagColor as TagColor")
Note added 6/7/13: the select clause does not require aliases - this works too:
.select("rights.*,tags.TagName,tags.TagColor")
Now I can reference TagName and TagColor in my view:
<% #rights.each do |right| %>
<tr ALIGN=Left <%=
# color background if this is tagged
" BGCOLOR=#{right.TagColor}" if right.TagColor
%> > ...
<% end %>
I don't think that you can load users and profiles with join in Rails. I think that in earlier versions of Rails ( < 2.1) loading of associated models was done with joins, but it was not efficient. Here you have some explanation and links to other materials.
So even if you explicite say that you want to join it, Rails won't map it to associated models. So if you say Profile.whatever_here it will always be mapped to Profile object.
If you still want to do what you said in question, then you can call custom sql query and process results by yourself:
p = ActiveRecord::Base.connection.execute("SELECT * FROM profiles JOIN users ON profiles.user_id = users.id LIMIT 1")
and get results row by row with:
p.fetch_row
It will already be mappet to an array.
Your errors are because you are calling first_name and user method on AciveRecord::Relation object and it stores an array of Profile objects, not a single object. So
p = Profile.joins(:user).limit(1)
p[0].first_name
shoud work.
Better way to fetch only one record is to call:
p = Profile.joins(:user).first
p.first_name
p.user
But when you call p.user it will query database. To avoid it, you can use include, but if you load only one profile object, it is useless. It will make a difference if you load many profiles at a time and want to inlcude users table.
Try using select("*").joins(:table)
In this case, you would type:
User.select("*").joins(:profile)
Hope that works for you.
After reading these tips I got the joins to all be loaded in one query by reading 3 ways to do eager loading (preloading) in Rails 3 & 4.
I'm using Rails 4 and this worked like a charm for me:
refs = Referral.joins(:job)
.joins(:referee)
.joins(:referrer)
.where("jobs.poster_id= ?", user.contact_id)
.order(created_at: :desc)
.eager_load(:job, :referee, :referrer)
Here were my other attempts.
#first attempt
#refs = Referral.joins(:job)
# .where("jobs.poster_id= ?", user.contact_id)
# .select("referrals.*, jobs.*")
# works, but each column needs to be explicitly referenced to be used later.
# also there are conflicts for columns with the same name like id
#second attempt
#refs = ActiveRecord::Base.connection.exec_query("SELECT jobs.id AS job_id, jobs.*, referrals.id as referral_id, referrals.* FROM referrals INNER JOIN jobs ON job_id = referrals.job_id WHERE (jobs.poster_id=#{user.contact_id});")
# this worked OK, but returned back a funky object, plus the column name
# conflict from the previous method remains an issue.
#third attempt using a view + rails_db_views
#refs = JobReferral.where(:poster_id => user.contact_id)
# this worked well. Unfortunately I couldn't use the SQL statement from above
# instead of jobs.* I had to explicitly alias and name each column.
# Additionally it brought back a ton of duplicate data that I was putting
# into an array when really it is nice to work with ActiveRecord objects.
#eager_load
#refs = Referral.joins(:job)
# .where("jobs.poster_id= ?", user.contact_id)
# .eager_load(:job)
# this was my base attempt that worked before I added in two more joins :)
I have got round this problem by creating a VIEW in the database which is the join, and then referencing that as if it were a normal ActiveRecord table in the code. This is fine for getting data out of the database, but if you need to update it, then you'll need to go back to the base classes that represent the 'real' tables. I have found this method to be handy when doing reports that use biggish tables - you can get the data out all in one hit. I am surprised that this doesn't seem to be built into ActiveRecord, seems an obvious thing to me!
So for you:
IN SQL:
CREATE VIEW User_Profiles
AS
SELECT P.*, U.first_name
FROM Users U
inner join Profiles P on U.id=P.user_id
IN RUBY models file:
class UserProfile < ActiveRecord::Base
self.primary_key = :id
#same dependencies as profiles
end
**HINT... I always forget to set the owner of the view (I use postgres), so it blows up straight away with much cursing and self-recrimination.
I've encountered the following error while trying to create a blogging application. Any ideas why?
NoMethodError in Articles#show
Showing app/views/articles/show.html.erb where line #1 raised:
undefined method `title' for []:Array
Extracted source (around line #1):
1: <h2><%= #article.title %></h2>
2:
3: <% if #article.category %>
4: <p class="category">
From my limited understanding it's trying to tell me that there is no 'title' field in my 'article' database table, however as you can see from the desc below there is cleary a 'title' field!
mysql> desc articles;
+--------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| user_id | int(11) | YES | | NULL | |
| title | varchar(255) | YES | | NULL | |
| synopsis | text | YES | | NULL | |
| body | text | YES | | NULL | |
| published | tinyint(1) | YES | | 0 | |
| created_at | datetime | YES | | NULL | |
| updated_at | datetime | YES | | NULL | |
| published_at | datetime | YES | | NULL | |
| category_id | int(11) | YES | | 1 | |
+--------------+--------------+------+-----+---------+----------------+
10 rows in set (0.01 sec)
Help?!
Bernard
Ps. hope the formatting of the table above holds up... doesn't seem to look very good in the preview!
Controller code for relevant call as follows.
def show
if is_logged_in? && #logged_in_user.has_role?('Editor')
#article = Article.find(params[:id])
else
#article = Article.find_all_by_published(params[:id], true)
end
respond_to do |wants|
wants.html
wants.xml { render :xml => #article.to_xml }
end
end
I think you're trying to access the title element directly from the array. You'll need to iterate through each of the objects before you can access the properties.
for #article in #articles do |a|
<h2><%= a.title %></h2>...
end
Just make sure to have in your controller...
#articles = Article.find(:all, :conditions => '...')
Update:
This part of your code returns a collection.
#article = Article.find_all_by_published(params[:id], true)
It looks like you're assigning an empty array to #article in your controller. It should instead be an instance of Article (if that's your model name). Can you paste your controller code?