Fueling Curiosity, One Insight at a Time

In Ruby, public_send allows calling a method dynamically when its name is stored in a variable.

• Why Use public_send?
Instead of calling methods explicitly, we can determine the method name at runtime and call it dynamically.

Example: Handling Different Attribute Names

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

• If item has ordered_quantity, it calls item.ordered_quantity
• Otherwise, it calls item.quantity
• This avoids unnecessary if-else statements
#ruby

In Ruby, there are two ways to define hash keys:

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

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

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

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

In Ruby, attr_reader automatically creates a getter method for instance variables, making code cleaner and more concise. Instead of writing:

def some_number
  @some_number
end

You can simply use:

attr_reader :some_number

This makes attributes read-only while keeping the class lightweight

#ruby #CU6U0R822

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

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

'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

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

When testing with Capybara, you might need to scroll an element into view before interacting with it. Instead of using JavaScript like:

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

You can use Capybara's built-in method:

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

In JavaScript, you can use localeCompare with { sensitivity: "base" } to compare strings without considering case or accents.
Example:

"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

"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

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:

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

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.

<% 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.

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:

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:

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

The output will be:

[
  #<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:

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

If you use:

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:

params.permit(posts: [:id])

Will not enforce your expectation of the nested parameter structure and will accept it without validation.