Dmitry Voronov
How to use Rails translations for Reform attributes
If you use Reform for the form objects and want the translations in your Rails application to work as with ActiveRecord objects, then you can add ActiveModel::Translation module to the form class or base class and specify the method with the key to translations.
class BaseForm < Reform::Form
extend ActiveModel::Translation
def self.i18n_scope
:forms
end
end
class UserForm < BaseForm
feature Coercion
property :login
property :change_password, virtual: true, type: Types::Form::Bool
property :password
property :password_confirmation
validation do
required(:login).filled
end
validation if: ->(_) { change_password } do
required(:password).confirmation
end
end
Set translations for form fields.
You can move them to a new file config/locales/forms.yml.
en:
forms:
attributes:
user_form:
login: Enter login
change_password: Change password?
password: Enter password
password_confirmation: Confirm password
Now, translations will be used by the simple form or you can call them manually by UserForm.human_attribute_name.
How to store large JSON in PostgreSQL with Rails Attributes API
If you store large objects in the database (such as JSON), for example, data for big reports, then this can take up a lot of space. To reduce the size of data, you can compress and store in binary form.
PostgreSQL has a bytea field type for storing such data. You can add bytea column in Rails using migration
add_column :reports, :data, :binary
For binary field operations, you can use the Rails Attributes API and add a new BinaryHash data type
# app/types/binary_hash.rb
class BinaryHash < ActiveRecord::Type::Binary
def serialize(value)
super value_to_binary(value.to_json)
end
def deserialize(value)
super case value
when NilClass
{}
when ActiveModel::Type::Binary::Data
value_to_hash(value.to_s)
else
value_to_hash(PG::Connection.unescape_bytea(value))
end
end
private
def value_to_hash(value)
JSON.parse(
ActiveSupport::Gzip.decompress(value),
symbolize_names: true
) || {}
end
def value_to_binary(value)
ActiveSupport::Gzip.compress(value)
end
end
Register new type in initializers
# config/initializers/types.rb
ActiveRecord::Type.register(:binary_hash, BinaryHash)
And add to binary type attribute in model
# app/models/snapshot.rb
class Reports < ApplicationRecord
attribute :data, :binary_hash
end
Tests show that data size is reduced by almost 3 times
Run time with 100000 width JSON
user system total real
Compress JSON 0.008671 0.001535 0.010206 ( 0.010885)
Decompress JSON 0.001357 0.000095 0.001452 ( 0.001509)
json size 95450 bytes
binary size 33868 bytes
~ 2.82 times compression
A simple way to distribute jobs in Sidekiq queues
This option implies that jobs of one context are executed sequentially in one queue, and jobs of different contexts in parallel in different queues.
Let's look at the following example.
There are investment funds for which we want to make time-consuming reporting calculations. Jobs for calculation within the same fund are carried out sequentially so that there are no errors in the calculations, jobs of different funds are performed in parallel.
We automate the distribution of jobs in queues so as not to specify a queue manually.
Specify the queues in the sidekiq.yml configuration file:
:queues:
- fund_processor_0
- fund_processor_1
- fund_processor_2
- fund_processor_3
- fund_processor_4
It is important that the queues are numbered from 0.
Now, when starting the worker, we indicate in which queue we will set the job depending on the fund. To do this, we use the operation of obtaining the remainder from dividing the fund ID and the count of queues. So we get the queue number.
# 5 queues
# fund ID % count of queues = queue number
# 1 % 5 => 1
# 2 % 5 => 2
# 3 % 5 => 3
# 4 % 5 => 4
# 5 % 5 => 0
def queue_name(fund_id)
queue_number = fund_id % 5
"fund_processor_#{queue_number}"
end
Start the worker, indicating to him the received queue name.
This can be done using the Sidekiq API
Sidekiq::Client.push(
'queue' => queue_name(fund_id),
'class' => Fund::ReportCalculator,
'args' => [fund_id]
)
Create factory with an uploaded file in Rails rspec
To create a factory with an uploaded file in Rails rspec, needs to be included ActionDispatch::TestProcess module in the rails_helper.rb file to use the #fixture_file_upload method in the factories.
# spec/rails_helper.rb
include ActionDispatch::TestProcess
In a factory, when setting the attribute value, use the method #fixture_file_upload, specifying the path and file type.
# spec/factories/import_file.rb
FactoryBot.define do
factory :import_file, class: ImportFile do
data { fixture_file_upload 'spec/fixtures/test_file.pdf', 'application/pdf' }
end
end
How to delete polymorphic models cascade
If you use a polymorphic model in your Rails application, like in example
class Trade < ActiveRecord::Base
has_many :gl_entries, as: :source, dependent: :destroy
end
class GlEntry < ActiveRecord::Base
belongs_to :source, polymorphic: true
end
You will not be able to add the usual foreign keys for cascading delete records. But this can be implemented using a database.
To do this, you need to write a trigger in the database that will run the delete function for each record.
CREATE FUNCTION deleteGlEntriesOfTrade()
RETURNS TRIGGER
SET SCHEMA 'public'
LANGUAGE plpgsql
AS $$
BEGIN
DELETE FROM gl_entries WHERE source_id = OLD.id AND source_type = 'Trade';
RETURN OLD;
END;
$$;
CREATE TRIGGER deleteTradesGlEntriesTrigger
BEFORE DELETE ON trades
FOR EACH ROW EXECUTE PROCEDURE deleteGlEntriesOfTrade();
Create a migration and use :)
Use hash or case-statement in Ruby?
Often, when we need to get a value based on the other one, we're using a case-statement. Like this
def realizing_trade_type(realizable_trade_type)
case realizable_trade_type
when 'buy'
'sell'
when 'short'
'cover'
when 'buy_contract'
'sell_contract'
when 'short_contract'
'cover_contract'
end
end
But, if the conditions and the results are simple values, why don't we use hash for this? We can :)
REALIZING_TRADE_TYPES = {
'buy' => 'sell',
'short' => 'cover',
'buy_contract' => 'sell_contract',
'short_contract' => 'cover_contract'
}.freeze
Here is the benchmark of both options, executed 10000000 times. It shows that a hash is faster in times for such the kind of usage.
>> require 'benchmark'
true
>> Benchmark.bm(15) do |x|
x.report('hash') { 10_000_000.times { REALIZING_TRADE_TYPES['buy'] } }
x.report('case-statement') { 10_000_000.times { realizing_trade_type 'buy' } }
x.report('empty') { 10_000_000.times {} }
end
user system total real
hash 0.990423 0.003412 0.993835 ( 1.057612)
case-statement 1.752263 0.004531 1.756794 ( 1.762030)
empty 0.380810 0.000728 0.381538 ( 0.382153)
So, it's better to use a hash when you are just retrieving some values (like in the example above). If there is additional logic to execute, a case-statement is still a way to go.
Render and combine PDF files into one
Render PDF files from HTML templates in Rails can be done using WickedPDF.
First you need to use ActionView to render HTML to a string:
def render_to_string(data)
action_view = ActionView::Base.new
action_view.view_paths = ActionController::Base.view_paths
action_view.class_eval do
include ApplicationHelper
include PDFHelper
# or other helpers
end
action_view.render template: 'pdf/template.html',
layout: 'layout/pdf.html',
locals: { data: data }
end
Then you can render pdf with the desired settings like this:
# first pdf file with some view settings and values from data1...
pdf1 = WickedPdf.new.pdf_from_string(
render_to_string(data1), {
pdf: 'report1',
page_size: 'Letter',
orientation: 'Portrait'
})
# ...and second pdf file with some view settings and values from data2
pdf2 = WickedPdf.new.pdf_from_string(
render_to_string(data2), {
pdf: 'report2',
page_size: 'Letter',
orientation: 'Landscape'
})
And now you can combine it with CombinePDF gem, that provide you parse method to get PDF content and to_pdfmethod to render the result back to PDF.
combiner = CombinePDF.new
combiner << CombinePDF.parse(pdf1)
combiner << CombinePDF.parse(pdf2)
combiner.to_pdf
Use image files from S3 in WickedPdf
If you need to use image files from S3 in your generated pdf file using WickedPdf, then you need first to download the image. You can create method that does this and add it to the helper.
require 'open-uri'
module PdfHelper
def embed_remote_image(url, content_type)
asset = open(url, "r:UTF-8", &:read)
base64 = Base64.encode64(asset.to_s).gsub(/\s+/, "")
"data:#{content_type};base64,#{Rack::Utils.escape(base64)}"
end
end
And use image_tag instead of wicked_pdf_image_tag
= image_tag embed_remote_image(file.logo_url, 'image/jpeg')
Manage Elixir versions like RVM & Rbenv
You can install different versions of the Elixir with help of Kiex, like in Ruby with a RVM and Rbenv.
Download and install Kiex
\curl -sSL https://raw.githubusercontent.com/taylor/kiex/master/install | bash -s
```bash
In .bashrc (or .zshrc if you use z shell), add the following
```bash
[[ -s "$HOME/.kiex/scripts/kiex" ]] && source "$HOME/.kiex/scripts/kiex"
```bash
Install required Elixir
```bash
kiex install 1.7 # or another version
```bash
And then you can use any version
```bash
kiex use 1.7
```bash
How to create zip files on the fly w/o Tempfile
There are many articles about how to archive files from the server and send a zip-file to a client without persisting it on the server. But usually they don't literally do it, because they use temporary files.
There is a simple way to do it without creating any file though. You just have to put files directly to Zip::OutputStream and then read from it. Btw pay attention: you must rewind the stream before reading it.
# some files objects
def download(files)
zip_stream = Zip::OutputStream.write_buffer do |zip|
files.each.with_index(1) do |file, index|
# file name must be uniq in archive
zip.put_next_entry("#{file.name}--#{index}.#{file.extension}")
zip.write(file.read.force_encoding('utf-8'))
end
end
# important - rewind the steam
zip_stream.rewind
send_data zip_stream.read,
type: 'application/zip',
disposition: 'attachment',
filename: 'files-archive.zip'
end