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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
Author
user-image
Nived Hari
System Analyst
In Ruby, there are two ways to define hash keys:

1. Using the Colon Syntax (:) – Creates a Literal Symbol Key

Code

item.update!(
  ordered_quantity: new_quantity,
)


Key Behavior: The key is treated as a fixed symbol (e.g., :ordered_quantity).

2. Using the Hash Rocket (=>) – Evaluates the Left-Hand Side as a Key

Code

item.update!(
  quantity_field => new_quantity,
)


Key Behavior: The left-hand side is evaluated dynamically, making it useful for variable-based keys.

Example Use Case: Dynamic Keys

Code

quantity_field = item.respond_to?(:ordered_quantity) ? :ordered_quantity : :quantity
new_quantity = item.public_send(quantity_field).to_i + item_case[:quantity].to_i

item.update!(
  quantity_field => new_quantity,  # Evaluates to :ordered_quantity or :quantity
)


Here, quantity_field is determined dynamically based on the model, so => must be used instead of :.

When to Use =>?
• When working with multiple models that have different column names
• When dynamically generating hash keys at runtime
• When building flexible APIs that handle varying attribute names
Takeaway:
• Use : when the key is static and always the same.
• Use => when the key is stored in a variable or needs to be evaluated dynamically.
#ruby
Published
Author
user-image
Nived Hari
System Analyst
In Ruby, attr_reader automatically creates a getter method for instance variables, making code cleaner and more concise. Instead of writing:

Code

def some_number
  @some_number
end


You can simply use:

Code

attr_reader :some_number


This makes attributes read-only while keeping the class lightweight

#ruby #CU6U0R822
Published
Author
user-image
Nitturu Baba
System Analyst
Real-time AI response streaming improves user experience by reducing wait times and making interactions feel more dynamic. Instead of waiting for the entire response to be generated before displaying it, streaming allows data to be processed and presented incrementally.

Example of AI response streaming using Nest Js backend and Next JS front end.

Setting Up the NestJS Backend for Streaming AI Responses

Controller


Code

import { Controller, Post, Body, Res } from '@nestjs/common';
import { openai } from '@ai-sdk/openai';
import { streamText } from 'ai';
import { Response } from 'express';

@Controller('orchestrator')
export class OrchestratorController {

 @Post('chat')
 async chat(@Body() payload: any, @Res() res: Response) {
  const { messages } = payload;

  const result = streamText({
   model: openai('gpt-4o'),
   messages,
  });
   
  result.pipeDataStreamToResponse(res); // Streams the AI response directly to the client
 }
}


How It Works
• The @Post('chat') endpoint listens for chat requests.
• The streamText function sends user messages to OpenAI and receives a streamed response.
• pipeDataStreamToResponse(res) directly streams the AI-generated content to the client as it arrives.
Building the Next.js Frontend for AI Response Streaming

chat/page.tsx


Code

'use client';

import { useChat } from '@ai-sdk/react';

export default function Home() {
 const { messages, input, handleInputChange, handleSubmit } = useChat({
  api: 'https://localhost:3000/api/orchestrator/chat',  // make the post request to the NestJS backend
 });

 return (
  <div>
   {messages.map((message) => (
    <div key={message.id}>
     {message.role === 'user' ? 'User: ' : 'AI: '}
     {message.content}
    </div>
   ))}

   <form onSubmit={handleSubmit}>
    <input
     name="prompt"
     value={input}
     onChange={handleInputChange}
     className="text-black"
    />
    <button type="submit">Submit</button>
   </form>
  </div>
 );
}


How It Works
• The useChat hook from AI-SDK manages state and streaming logic automatically.
• It sends user messages to the backend and updates the UI in real time as responses arrive.
• The messages array dynamically updates, displaying each chunk of AI-generated text as it's received.
#C08DPTN3JAW #streaming #next js #nest js
Published
Author
user-image
Puneeth kumar
System Analyst
Collection caching is a way to speed up rendering multiple items on a page by storing their HTML in cache.
How it works:
1. When we use <%= render partial: 'products/product', collection: @products, cached: true %>, Rails checks if each product's HTML is already stored in the cache.
2. If a product’s HTML is found in the cache, Rails loads it quickly instead of rendering it again.
3. If a product’s HTML is not in the cache, Rails will render it, store it in the cache, and use it next time.
4. The big advantage: Rails fetches all cached products at once (instead of one by one), making it much faster.
#CU6U0R822 #caching #collection_caching
Published
Author
user-image
Nived Hari
System Analyst
When testing with Capybara, you might need to scroll an element into view before interacting with it. Instead of using JavaScript like:

Code

page.execute_script("arguments[0].scrollIntoView(true)", button)


You can use Capybara's built-in method:

Code

scroll_to(button)  # Scrolls to the element


This is available in
Capybara 3.26+
and is the preferred way to ensure visibility before clicking or interacting with an element.

#capybara #CU6U0R822 #C041BBLJ57G
Published
Author
user-image
Nived Hari
System Analyst
In JavaScript, you can use localeCompare with { sensitivity: "base" } to compare strings without considering case or accents.
Example:


Code

"Test".localeCompare("test", undefined, { sensitivity: "base" }) === 0; // ✅ True
"café".localeCompare("cafe", undefined, { sensitivity: "base" }) === 0; // ✅ True
"Hello".localeCompare("HELLO", undefined, { sensitivity: "base" }) === 0; // ✅ True


• Case-insensitive
• Accent-insensitive
No need for toLowerCase() hacks anymore! 🎉

second argument is locale . by giving it as "Undefined" it uses default locale of the runtime environment. We can specify as "en", "id" etc. It is used in sorting scenarios ig.

Sensitivity is the behaviour of the comparison


Code

"base" → Ignores case & accents ("café" == "cafe", "Hello" == "hello")

"accent" → Considers accents but ignores case ("café" != "cafe", "Hello" == "hello")

"case" → Considers case but ignores accents ("café" == "cafe", "Hello" != "hello")

"variant" → Considers both case & accents ("café" != "cafe", "Hello" != "he



#stimulus #JavaScript #StringComparison
Published
Author
user-image
Nived Hari
System Analyst
By default, Capybara only finds visible and interactable elements. If a button is disabled or outside the viewport, Capybara may fail to locate it.
To fix this, use:


Code

expect(page).to have_button("Add Discrepancy", disabled: true, visible: :all)


• disabled: true ensures the button is actually disabled
• visible: :all allows Capybara to find buttons that are hidden, off-screen, or disabled
This is useful when testing UI behaviors where buttons are conditionally enabled/disabled or require scrolling to be visible.

#CU6U0R822 #capybara #C041BBLJ57G #specs
Published
Author
user-image
Puneeth kumar
System Analyst
local_assigns :
When using partial views in Rails (like _partial.html.erb), we might pass local variables to customize the rendering. However, if we try to use a local variable that wasn't passed, Rails will raise an error.
To avoid this, local_assigns is a special hash that helps check if a local variable was provided when rendering the partial. Instead of directly using <%= show_projects %>, which could cause an error if missing, we can safely check local_assigns[:show_projects] first.


Code

<% if local_assigns[:show_projects] %> 
  
    <%= (render @user.projects) || (render 'shared/empty_state', message: "No projects found!") %>
   
<% end %>


Here, the partial checks if show_projects was passed before using it. If show_projects was provided, it renders the user's projects or a message if no projects are found. If show_projects wasn't passed, nothing happens, preventing errors.
Published
Author
user-image
Mohammad hussain
System Analyst
The Rails 8.0 release introduces several new features, and among them, params#expect stands out.

In our daily work with Rails, we often rely on params#require for assignments and queries. However, params#require is more explicit than permit. Here’s an example to illustrate:


Code

params = ActionController::Parameters.new(posts: [{id: 1}])


If you expect the posts parameter to contain a list of IDs, such as [{id: 1}, {id: 2}], you can define your expectations like this:


Code

params.expect(posts: [[:id]])


The output will be:

Code

[
  #<ActionController::Parameters {"id"=>1} permitted: true>,
  #<ActionController::Parameters {"id"=>2} permitted: true>
]


Now, consider a different scenario where you expect the posts parameter to have only a single hash with an ID, like this:


Code

params = ActionController::Parameters.new(posts: {id: 1})


If you use:


Code

params.expect(posts: [[:id]])


It will raise the following error:

ActionController::ExpectedParameterMissing: param is missing or the value is empty or invalid: posts
In contrast, using the older params#permit:


Code

params.permit(posts: [:id])


Will not enforce your expectation of the nested parameter structure and will accept it without validation.
Published
Author
user-image
Giritharan
System Analyst
Rails Inflections:
What is it? Inflections in Rails, powered by the ActiveSupport::Inflector module, allow customization of how words are pluralized, singularized, or treated as uncountable.
Why use it? Sometimes Rails' default pluralization rules don't fit your app's needs (e.g., irregular words like foot → feet, uncountable words like milk).

Examples

• Default Behavior:

Code

"person".pluralize  # => "people"
"person".singularize # => "person"


• Irregular Inflections:

Code

ActiveSupport::Inflector.inflections(:en) do |inflect|
  inflect.irregular "foot", "feet"
end

// "foot".pluralize  # => "feet"


• Uncountable Words:

Code

ActiveSupport::Inflector.inflections(:en) do |inflect|
  inflect.uncountable "milk"
end

// "milk".pluralize  # => "milk"


• Acronym Inflections:

Code

ActiveSupport::Inflector.inflections(:en) do |inflect|
  inflect.acronym "HTML5"
end

// "html5".camelize  # => "HTML5"


Potential Issues:
• Default Behavior May Be Inaccurate: Without customizing, words like "tooth" become "tooths" or "milk" becomes "milks."
• Localization: Inflections are locale-specific, so customizations for one locale won't apply to others.
Best Practice: Always define rules for edge cases (irregular, uncountable, acronyms) in your config/initializers/inflections.rb ans restart the server after changes

#rails-inflections #active-support #CU6U0R822

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