TILs - Fueling Curiosity, One Insight at a Time

At Codemancers, we believe every day is an opportunity to grow. This section is where our team shares bite-sized discoveries, technical breakthroughs and fascinating nuggets of wisdom we've stumbled upon in our work.

Published: Aug 6, 2024
Author: Sujay

Rails templates accept any locals as arguments. However, starting from Rails 7.1, we can restrict which locals a template must accept using "Strict Locals".

Code

// _search.html.erb

<# locals: (:url, :field_name, :placeholder) -%>

We can also set default values

Code

<# locals: (placeholder: "Search", :url, :field_name) -%>

#rails

Published: Aug 3, 2024
Author: Adithya Hebbar
System Analyst

Detecting a mobile browser using regex.

You can use regex which returns a true or false value depending on whether or not the user is browsing with a mobile. WOW!

JavaScript

window.mobilecheck = function () {
  var mobileCheck = false;
  (function (a) {
    if (
      /(android|bb\\d+|meego).+mobile|avantgo|bada\\/|blackberry|blazer|compal|elaine|fennec|hiptop|iemobile|ip(hone|od)|iris|kindle|lge |maemo|midp|mmp|mobile.+firefox|netfront|opera m(ob|in)i|palm( os)?|phone|p(ixi|re)\\/|plucker|pocket|psp|series(4|6)0|symbian|treo|up\\.(browser|link)|vodafone|wap|windows ce|xda|xiino/i.test(
        a
      ) ||
      /1207|6310|6590|3gso|4thp|50[1-6]i|770s|802s|a wa|abac|ac(er|oo|s\\-)|ai(ko|rn)|al(av|ca|co)|amoi|an(ex|ny|yw)|aptu|ar(ch|go)|as(te|us)|attw|au(di|\\-m|r |s )|avan|be(ck|ll|nq)|bi(lb|rd)|bl(ac|az)|br(e|v)w|bumb|bw\\-(n|u)|c55\\/|capi|ccwa|cdm\\-|cell|chtm|cldc|cmd\\-|co(mp|nd)|craw|da(it|ll|ng)|dbte|dc\\-s|devi|dica|dmob|do(c|p)o|ds(12|\\-d)|el(49|ai)|em(l2|ul)|er(ic|k0)|esl8|ez([4-7]0|os|wa|ze)|fetc|fly(\\-|_)|g1 u|g560|gene|gf\\-5|g\\-mo|go(\\.w|od)|gr(ad|un)|haie|hcit|hd\\-(m|p|t)|hei\\-|hi(pt|ta)|hp( i|ip)|hs\\-c|ht(c(\\-| |_|a|g|p|s|t)|tp)|hu(aw|tc)|i\\-(20|go|ma)|i230|iac( |\\-|\\/)|ibro|idea|ig01|ikom|im1k|inno|ipaq|iris|ja(t|v)a|jbro|jemu|jigs|kddi|keji|kgt( |\\/)|klon|kpt |kwc\\-|kyo(c|k)|le(no|xi)|lg( g|\\/(k|l|u)|50|54|\\-[a-w])|libw|lynx|m1\\-w|m3ga|m50\\/|ma(te|ui|xo)|mc(01|21|ca)|m\\-cr|me(rc|ri)|mi(o8|oa|ts)|mmef|mo(01|02|bi|de|do|t(\\-| |o|v)|zz)|mt(50|p1|v )|mwbp|mywa|n10[0-2]|n20[2-3]|n30(0|2)|n50(0|2|5)|n7(0(0|1)|10)|ne((c|m)\\-|on|tf|wf|wg|wt)|nok(6|i)|nzph|o2im|op(ti|wv)|oran|owg1|p800|pan(a|d|t)|pdxg|pg(13|\\-([1-8]|c))|phil|pire|pl(ay|uc)|pn\\-2|po(ck|rt|se)|prox|psio|pt\\-g|qa\\-a|qc(07|12|21|32|60|\\-[2-7]|i\\-)|qtek|r380|r600|raks|rim9|ro(ve|zo)|s55\\/|sa(ge|ma|mm|ms|ny|va)|sc(01|h\\-|oo|p\\-)|sdk\\/|se(c(\\-|0|1)|47|mc|nd|ri)|sgh\\-|shar|sie(\\-|m)|sk\\-0|sl(45|id)|sm(al|ar|b3|it|t5)|so(ft|ny)|sp(01|h\\-|v\\-|v )|sy(01|mb)|t2(18|50)|t6(00|10|18)|ta(gt|lk)|tcl\\-|tdg\\-|tel(i|m)|tim\\-|t\\-mo|to(pl|sh)|ts(70|m\\-|m3|m5)|tx\\-9|up(\\.b|g1|si)|utst|v400|v750|veri|vi(rg|te)|vk(40|5[0-3]|\\-v)|vm40|voda|vulc|vx(52|53|60|61|70|80|81|83|85|98)|w3c(\\-| )|webc|whit|wi(g |nc|nw)|wmlb|wonu|x700|yas\\-|your|zeto|zte\\-/i.test(
        a.substr(0, 4)
      )
    )
      mobileCheck = true;
  })(navigator.userAgent || navigator.vendor || window.opera);
  return mobileCheck;
};

I wonder who in the world wrote this snippet!!! :)

#javascript #browser

Published: Aug 2, 2024
Author: Syed

Ransack adds several class methods to ActiveRecord::Base for managing search and sort capabilities. These methods allow us to define which attributes, associations, and scopes are accessible through Ransack queries, thus enhancing security and control.

ransackable_attributes: Defines which model attributes can be used in Ransack searches.
For example, only the order_number, status, and business_unit fields can be used in Ransack searches.

Code

def self.ransackable_attributes(auth_object = nil)
    %w[order_number status business_unit]
  end

ransackable_associations: Specifies which model associations are accessible for searching.
For examle, only the customer and vendor associations are allowed for searching.

Code

def self.ransackable_associations(auth_object = nil)
    %w[customer vendor]
  end

ransortable_attributes: Lists which attributes can be used for sorting results.
In this example, sorting is allowed only by order_number and created_at

Code

def self.ransortable_attributes(auth_object = nil)
    %w[order_number created_at]
  end

ransackable_scopes: Determines which custom scopes can be applied in searches.

#rails #ransack #search

Published: Aug 2, 2024
Author: Sujay

In postgres, current_setting() function is used to get the value of a configuration parameter.

Code

Set rls.tenant_id = 1;
SET

select current_setting('rls.tenant_id');
 current_setting
-----------------
 1
(1 row)

#postgres

Published: Jul 31, 2024
Author: Syed

Namespaces in Rails help organize our application by grouping related controllers, models, and views into separate directories. Using namespaces with scaffolding keeps our codebase structured and manageable, especially in larger applications.

Example.
rails generate scaffold Order::PurchaseOrder order_number:string business_unit:string ...

This will create files under the Order namespace, including controllers, models, and views. This approach keeps our codebase structured, with Order as a namespace, making it easier to manage related components and maintain clarity in larger applications.

Ruby

app/
├── controllers/
│   └── order/
│       └── purchase_orders_controller.rb
├── models/
│   └── order/
│       └── purchase_order.rb
├── views/
│   └── order/
│       └── purchase_orders/
│           ├── _form.html.erb
│           ├── edit.html.erb
│           ├── index.html.erb
│           ├── new.html.erb
│

#rails #namespace

Published: Jul 30, 2024
Author: Vaibhav Yadav
Senior System Analyst

Cross browser regular expression issue:

Recently I came across a regular expression that would cause the page to crash on iphone Safari browser, the regex was for obscuring email.

Problematic Regex:

JavaScript

const obscuredEmail = email.replace(/(?<=.1}).(?=[^@]*@)/g, '*');

Fix:

JavaScript

const obscuredEmail = email.replace(/(.)(?=.*@)/g, (match, p1, offset, string) => offset < string.indexOf('@') - 1 ? '*' : p1);

Lesson: Even a browser can cause browser compatibility issues.

#regex #browserCompatibility #safari #javascript

Published: Jul 29, 2024
Author: Sachin Kabadi
System Analyst

How to override models in parent application by reopening existing Rails engine classes. This can be done by organising overrides in a dedicated directory (e.g., app/overrides), ignoring this directory in the autoloader, and preloading the overrides in a to_prepare callback.

Ruby

# config/application.rb
module MyApp
  class Application < Rails::Application
    # ...

    overrides = "#{Rails.root}/app/overrides"
    Rails.autoloaders.main.ignore(overrides)

    config.to_prepare do
      Dir.glob("#{overrides}/**/*_override.rb").sort.each do |override|
        load override
      end
    end
  end
end

To override an engine model, such as Blog::Article:

Ruby

# Blog/app/models/blog/article.rb
module Blog
  class Article < ApplicationRecord
    # ...
  end
end

Create a file that reopens the class:

Ruby

# MyApp/app/overrides/models/blog/article_override.rb
Blog::Article.class_eval do
  # ...
end

Using class_eval ensures we are reopening the class or module, not redefining it.

#rails #rails-engines

Published: Jul 25, 2024
Author: Sujay

Remove the published gem from rubygems using

Ruby

gem yank GEM -v VERSION

#rails #rubygems

Published: Jul 25, 2024
Author: Satya

while using form.file_field for file attachments we can restrict the file type to any type if we want.
For eg: if we want to accept file of type image then we can pass accept attribute.

Code

<%= form.file_field :picture, accept: "image/*" %>

Note: This will disable other file types in your local file dialog while enabling the image files only 🪄 .
#rails , #active-storage

Published: Jul 25, 2024
Author: Sujay

To ensure a dependency is installed with the engine during gem install, it must be specified within the Gem::Specification block inside the engine's .gemspec file (e.g., blog.gemspec for an engine named Blog, located at the root)

Code

s.add_dependency "pagy"

#rails #rails-engines

Published: Jul 23, 2024
Author: Syed

In Rails, gems are libraries that add specific functionality to a Rails application. They can be used across different projects and typically do not have their own structure or generators.
Examples include devise for authentication and nokogiri for XML parsing.

Engines, on the other hand, are miniature Rails applications that can have their own routes, controllers, models, and views. They are used to encapsulate and modularize specific features or components within a Rails app. An engine can be packaged as a gem, but it provides more extensive, self-contained functionality compared to a typical gem.

#rails

Published: Jul 19, 2024
Author: Sujay

A Rails engine is a pattern used to modularize a Rails application. These engines are self-contained applications with their own models, views, controllers, and routes, allowing them to function autonomously. They can be integrated into a larger Rails application. For example, in an e-commerce application, modules like orders, products, users, and payments can each be separate engines.
#rails

Published: Jul 19, 2024
Author: Codemancers

Resolving gen_random_uuid() Error with PostgreSQL While Implementing CI
When configuring CI with GitHub Actions, I encountered the following error:

Code

PG::UndefinedFunction: ERROR:  function gen_random_uuid() does not exist

This error occurred because the gen_random_uuid() function is not available in PostgreSQL versions older than 11. UUID generation functions were only available through external modules like uuid-ossp and pgcrypto in these older versions.

To resolve this issue, I upgraded to PostgreSQL 13, which includes the gen_random_uuid() function to generate version-4 UUIDs. After upgrading, the error was resolved.

#rails #postgresql #uuid #ci-cd #github-actions

Published: Jul 17, 2024
Author: Adithya Hebbar
System Analyst

Jupyter Labs

• To install Jupyter Labs in Mac using Homebrew:

Python

brew install jupyterlab

• To run Jupyter lab:

Python

jupyter lab

This will open JupyterLab in your default web browser.

#python #homebrew

Published: Jul 16, 2024
Author: Giritharan
System Analyst

The fields_for helper in Rails creates form bindings without rendering a <form> tag. This is particularly useful for rendering fields for additional model objects within a single form.

Imagine you have a Book model with an associated Author model. You can create a single form for both the Book and Author models using the fields_for helper.

Ruby

<%= form_with model: @book do |book_form| %>
  <%= book_form.text_field :title %>
  <%= book_form.text_area :description %>

  <%= fields_for :author, @book.author do |author_form| %>
    <%= author_form.text_field :name %>
    <%= author_form.text_field :email %>
  <% end %>
<% end %>

#rails #fields-for #rails-view

Published: Jul 16, 2024
Author: Codemancers

rails db:prepare in Ruby on Rails, This command sets up and prepares the database for my application, ensuring everything's ready to go, including populating the database.
#rails #databasesetup

Published: Jul 15, 2024
Author: Soniya Rayabagi

Handling Terraform State Errors with S3 Backend:
We use an S3 bucket to store our Terraform state. If Terraform fails to update the state, it creates an errored.tfstate file in your working directory. Reapplying will cause errors because the resources already exist.
To fix this, push the errored state back to S3:
terraform state push errored.tfstate

#devops #terraformstateS3 #errorhandling

Published: Jul 12, 2024
Author: Syed

In Ruby, exception handling is done using begin, rescue, ensure, and end blocks. Here's a brief overview of how they work in a general Ruby context:

Ruby

begin
  # Code that might raise an exception
rescue SomeExceptionClass => e
  # Code that handles the exception
ensure
  # Code that will always run, regardless of whether an exception was raised
end

begin: Marks the beginning of a block of code that might raise exceptions.

rescue: Specifies what to do if a specific exception is raised. We can rescue multiple exception types by chaining rescue blocks.

ensure: An optional block that will always execute, regardless of whether an exception was raised or rescued. It's useful for cleanup code that must run no matter what.

#ruby #rails

Published: Jul 12, 2024
Author: Syed

Using Ruby's built-in URI::MailTo::EMAIL_REGEXP for email validation is generally better than using a custom regular expression due to its robustness, reliability, and maintenance by the Ruby core team.

Ruby

class User < ApplicationRecord
  has_secure_password
  validates :name, presence: true

  # Using a custom regular expression for email validation
  validates :email, presence: true, format: { with: /\\A[^@\\s]+@[^@\\s]+\\z/ }, uniqueness: true
  
  # Using Ruby's built-in URI::MailTo::EMAIL_REGEXP for email validation
  validates :email, presence: true, format: { with: URI::MailTo::EMAIL_REGEXP }, uniqueness: true

end

#ruby #regex #rails

Published: Jul 12, 2024
Author: Syed

Fixing Image Rendering in Rails with Active Storage
How to fix the error PG::UndefinedTable: ERROR: relation "active_storage_attachments" does not exist

This error occurs because Active Storage in Rails relies on specific database tables (e.g., active_storage_attachments and active_storage_blobs) to store metadata about attached files. If these tables do not exist, Rails cannot store or retrieve the necessary metadata for file attachments, resulting in the mentioned error.

By following these steps, we ensure that the necessary Active Storage tables are created, allowing Rails to store and retrieve image metadata correctly.

Run Active Storage Installation:

Ruby

rails active_storage:install

Migrate the Database:

Ruby

rails db:migrate

Restart the Rails Server:

Ruby

rails server

Then in views we can simply use the helper and render the image

Ruby

<%= image_tag url_for(recipe.image), class: "w-full h-64 object-cover" %>

#rails #activestorage

Showing page 10 of 42

Your competitors are already using AI.
The question is how fast you want to unlock the value.

Don't know where to start?

AI is everywhere but it's unclear which investments will actually move your metrics and which are expensive experiments.

Your data isn't ready

Most AI projects fail at the data layer. Pipelines, quality, access all need work before LLMs can deliver value.

Internal teams are stretched

Your engineers are shipping product. They don't have capacity to also become AI specialists with production-grade experience.

Legacy systems block everything

Aging, undocumented codebases make AI integration slow, risky, and expensive. They need to move first.

Don't worry. We've got you covered.

Start with the audit.

Book a free discovery call →

TILs - Fueling Curiosity, One Insight at a Time

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JavaScript

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Ruby

Ruby

Ruby

Ruby

Ruby

Ruby

Your competitors are already using AI.The question is how fast you want to unlock the value.

Don't know where to start?

Your data isn't ready

Internal teams are stretched

Legacy systems block everything

Don't worry. We've got you covered.

Your competitors are already using AI.
The question is how fast you want to unlock the value.