I would like to update all records in a rails (3.1) model when i update an attribute on a single record.
Like self.update_attribute(:global_order => 1) then before or after save a would like to update all other records to update thier global_order (1, 2, 3, 4).
Right now with on after_save callback I get caught in a recursive loop, is skip callbacks the way to go? I would like the app to throw exceptions if anything seems strange in global_order.
Or are there any 3.1 gems that would solve my issue.
after_save :set_global_order
def set_global_order
#products = self.class.all(:order => :global_order)
#products.sort! {|a,b| a.global_order <=> b.global_order}
#products.reverse!
#products.each_with_index do |p, index|
p.update_attributes!({:global_order => index + 1})
end
end
Not sure if there's a gem, but you could definitely refactor this with the following considerations:
No need to pollute the object with an instance variable when a local one will do
The first three lines are sorting the same set, why not do that once?
...
def set_global_order
products = self.class.order('global_order DESC')
products.each_with_index do |p, index|
p.update_column(:global_order, index + 1)
end
end
Related
My application monitors ProductionJobs, derived from BusinessProcesses in successive versions. Thus the unique key of ProductionJob class is composed of business_process_id and version fields.
Initially, the ProductionJob index would display the list of objects (including all versions) using an Arel structured query (#production_jobs).
But it is more convinient to only show the last version of each ProductionJob. So I created a query (#recent_jobs) to retrieve the last version of the ProductionJob for a given BusinessProces.
Joining the 2 queries should return only the last version of each ProductionJob. This is what I can't achieve with my knowledge of Arel, and I would be grateful if you could show me how to do!
Here is the code in production_jobs_controller:
a) Arel objects setup
private
def jobs
ProductionJob.arel_table
end
def processes # jobs are built on the processes
BusinessProcess.arel_table
end
def flows # flows provide a classifiaction to processes
BusinessFlow.arel_table
end
def owners # owner of the jobs
User.arel_table.alias('owners')
end
def production_jobs # job index
jobs.
join(owners).on(jobs[:owner_id].eq(owners[:id])).
join(processes).on(jobs[:business_process_id].eq(processes[:id])).
join(flows).on(processes[:business_flow_id].eq(flows[:id])).
join_sources
end
def job_index_fields
[jobs[:id],
jobs[:code].as("job_code"),
jobs[:status_id],
jobs[:created_at],
jobs[:updated_by],
jobs[:updated_at],
jobs[:business_process_id],
jobs[:version],
processes[:code].as("process_code"),
flows[:code].as("statistical_activity_code"),
owners[:name].as("owner_name")]
end
def order_by
[jobs[:code], jobs[:updated_at].desc]
end
# Latest jobs
def recent_jobs
jobs.
join(owners).on(jobs[:owner_id].eq(owners[:id])).
join_sources
end
def recent_jobs_fields
[ jobs[:code],
jobs[:business_process_id].as('bp_id'),
jobs[:version].maximum.as('max_version')
]
end
b) The index method
# GET /production_jobs or /production_jobs.json
def index
#production_jobs = ProductionJob.joins(production_jobs).
pgnd(current_playground).
where("business_flows.code in (?)", current_user.preferred_activities).
order(order_by).
select(job_index_fields).
paginate(page: params[:page], :per_page => params[:per_page])
#recent_jobs = ProductionJob.joins(recent_jobs).select(recent_jobs_fields).group(:business_process_id, :code)
#selected_jobs = #production_jobs.joins(#recent_jobs).where(business_process_id: :bp_id, version: :max_version)
Unfortunately, #selected_jobs returns a nil object, even though #production_jobs and #recent_jobs show linkable results. how should I build the #selected_jobs statement to reach the expected result?
Thanks a lot!
After several trials, I finally included the sub-request in a 'where ... in()' clause. This may not be optimal, and I am open to other proposals.
The result can be understood as the following:
#recent_jobs provide the list ProductionJobs'last versions, based on their code and version
#production_jobs provide the list of all ProductionJobs
#selected_jobs adds the where clause to #production_jobs, based on the #recent_jobs:
The last request is updated to:
#selected_jobs = #production_jobs
.where("(production_jobs.code,
production_jobs.business_process_id,
production_jobs.version)
in (?)",
#recent_jobs
)
It works this way, but I'd be glad to receive suggestions to enhance this query. Thanks!
In Rails, I have a Product model. Sometimes I need to get multiple products at the same time (but the list is completely dynamic, so it can't be done on the Rails side).
So, let's say for this call I need to get products 1, 3, 9, 24 in one call. Is this possible? If so, do I need a custom route for this and what do I put in my controller?
i.e. does something like this work? /products/1,3,9,24
I don't think you should need to change the routes at all. You should just have to parse them in your controller/model.
def show
#products = Product.find params[:id].split(',')
end
If you then send a request to http://localhost/products/1,3,9,24, #products should return 4 records.
I would consider this a request to index with a limited scope, kind of like a search, so I would do:
class ProductsController < ApplicationController
def index
#products = params[:product_ids] ? Product.find(params[:product_ids]) : Product.all
end
end
and then link to this with a url array:
<%= link_to 'Products', products_path(:product_ids => [1, 2, 3]) %>
this creates the standard non-indexed url array that looks kind of like
product_ids[]=1&product_ids[]=2 ...
Hope that helps.
Product.where(:id => params[:ids].split(','))
On my Question model I have some scopes
scope :recent, order("created_at DESC")
scope :approved, where("status = ?", "approved")
scope :answered, approved.recent.where("answers_count > ?", 0)
On my question controller I'm retrieving questions using the scopes
example 1:
#questions = Question.approved.recent
example 2:
#questions = User.find(session[:user_id]).topics.map { |t| t.questions.approved.recent }.flatten.uniq
I'm trying to put will_paginate on my model to make things easier on the controller but the 2nd example is very tricky as it is using mapping to retrieve questions according to preferences.
I've tried to add this on my model
def self.pagination(page = 1)
self.paginate(:page => page, :per_page => 5)
end
and then on my controller I have
#questions = Question.approved.recent.pagination.(params[:page])
That works fine for the 1st example but I Dont know how to implement that on the 2nd example
Any hints?
This looks like Rails 3. Be sure to use the ~> 3.0.pre2 version of the will_paginate gem.
You can use the paginate method at the end of your chain of scopes. For example, your "example 1" would be:
#questions = Question.approved.recent.paginate(:page => params[:page], :per_page => 20)
I see you created a custom method (pagination) to wrap this pattern, but it's best that you keep this syntax in original form for now, especially since you're dealing with scopes and Relation objects in Rails 3 and will_paginate doesn't have proper support for this yet (but it's coming).
In your "example 2" it seems you only need to fetch the first few recent questions from each topic and that you won't perform a full-blown pagination here (like, going to page 2 and forward). You don't have to use the paginate method here; you can simply use ActiveRecord's limit:
current_user = User.find(session[:user_id])
#questions = current_user.topics.map { |topic|
topic.questions.approved.recent.limit(5).to_a
}.flatten.uniq
I have a create statement for some models, but it’s creating a record within a join table regardless of whether the record already exists.
Here is what my code looks like:
#user = User.find(current_user)
#event = Event.find(params[:id])
for interest in #event.interests
#user.choices.create(:interest => interest, :score => 4)
end
The problem is that it creates records no matter what. I would like it to create a record only if no record already exists; if a record does exist, I would like it to take the attribute of the found record and add or subtract 1.
I’ve been looking around have seen something called find_or_create_by. What does this do when it finds a record? I would like it to take the current :score attribute and add 1.
Is it possible to find or create by id? I’m not sure what attribute I would find by, since the model I’m looking at is a join model which only has id foreign keys and the score attribute.
I tried
#user.choices.find_or_create_by_user(:user => #user.id, :interest => interest, :score => 4)
but got
undefined method find_by_user
What should I do?
my_class = ClassName.find_or_initialize_by_name(name)
my_class.update_attributes({
:street_address => self.street_address,
:city_name => self.city_name,
:zip_code => self.zip_code
})
Assuming that the Choice model has a user_id (to associate with a user) and an interest_id (to associate with an interest), something like this should do the trick:
#user = User.find(current_user)
#event = Event.find(params[:id])
#event.interests.each do |interest|
choice = #user.choices.find_or_initialize_by_interest_id(interest.id) do |c|
c.score = 0 # Or whatever you want the initial value to be - 1
end
choice.score += 1
choice.save!
end
Some notes:
You don't need to include the user_id column in the find_or_*_by_*, as you've already instructed Rails to only fetch choices belonging to #user.
I'm using find_or_initialize_by_*, which is essentially the same as find_or_create_by_*, with the one key difference being that initialize doesn't actually create the record. This would be similar to Model.new as opposed to Model.create.
The block that sets c.score = 0 is only executed if the record does not exist.
choice.score += 1 will update the score value for the record, regardless if it exists or not. Hence, the default score c.score = 0 should be the initial value minus one.
Finally, choice.save! will either update the record (if it already existed) or create the initiated record (if it didn't).
find_or_create_by_user_id sounds better
Also, in Rails 3 you can do:
#user.choices.where(:user => #user.id, :interest => interest, :score => 4).first_or_create
If you're using rails 4 I don't think it creates the finder methods like it used to, so find_or_create_by_user isn't created for you. Instead you'd do it like this:
#user = User.find(current_user)
#event = Event.find(params[:id])
for interest in #event.interests
#user.choices.find_or_create_by(:interest => interest) do |c|
c.score ||= 0
c.score += 1
end
end
In Rails 4
You can use find_or_create_by to get an object(if not exist,it will create), then use update to save or update the record, the update method will persist record if it is not exist, otherwise update record.
For example
#edu = current_user.member_edu_basics.find_or_create_by(params.require(:member).permit(:school))
if #edu.update(params.require(:member).permit(:school, :majoy, :started, :ended))
Is there a pattern to refactor such a construct into a readable single line?
def show_section
#news = News.all_active
#news = #news.where(:section => params[:section]) unless params[:section] == "all"
#news = #news.all
end
I use Rails 3 and Ruby 1.9.2
#news = News.all_active.where(params[:section] == "all" ? nil : {:section => params[:section]})
You can get rid of #news.all - in Rails 3 query will be executed when you use the resulting ActiveRecord::Relation object (for example when you call each or first on it). Passing nil to where method will do nothing.
If all_active is a method, you can refactor it into a scope and then call it in a chain.
Great resources on Rails 3 queries:
Active Record Queries in Rails 3
Advanced Queries in Rails 3
Arel README
You can turn the where clause into a method on your News model:
class News
def self.for_section(section)
where(section == "all" ? nil : {:section => section})
end
end
Then in your controller, you can chain it all together like so:
News.for_section(params[:section]).all_active
This of course assumes that all_active is also a scope, and not a resultset.