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: Nov 4, 2024
Author: Anujeet Swain
System Analyst

Query Defaults in React-Query
Any option we pass to React-Query besides the query key can have its default values and can be set by following ways:
• Passing defaultOptions object to query client as global defaults.

Code

const queryClient = new QueryClient(
 defaultOptions: {
  queries: {
   staleTime: 10 * 1000
  }
 }
}

• Setting default options for subset of queries using Fuzzy Matching by setQueryDefaults method

Code

queryClient.setQueryDefaults(
 ['todos','list'],
 {staleTime: 10 * 1000}
) 
//This sets default stale time of 10secs for all the matched queries having keys 'todos' and 'list'

• Setting default options within useQuery for fine grain control over specific query.

Code

useQuery({
 queryKey: ['todo'],
 staleTime: 10 * 1000,
});

Each method takes precedence over the others in this order.
#react-query #customizing-defaults

Published: Nov 4, 2024
Author: Amber Srivastava

Promise.allSettled() :

Purpose: Executes multiple promises and waits for all of them to settle (either resolve or reject).
Returns: A promise that resolves with an array of objects. Each object has:
• status: Either "fulfilled" or "rejected".
• value: The resolved value (if fulfilled) or reason: The rejection reason (if rejected).
Example

Code

const promises = [
  Promise.resolve(1),
  Promise.reject('Error'),
  Promise.resolve(2),
];

Promise.allSettled(promises).then((results) => {
  results.forEach((result) => {
    if (result.status === 'fulfilled') {
      console.log('Result:', result.value);
    } else {
      console.log('Error:', result.reason);
    }
  });
});

Output :
Result: 1
Error: Error
Result: 2

#CCT1JMA0Z

Published: Oct 30, 2024
Author: Nitturu Baba
System Analyst

Git Rebase:

It is similar to merge, but the difference is merging brings the changes from the main branch into your current branch by creating a merge commit that combines the histories of both branches.

Rebasing applies your branch’s commits on top of the main branch, making it look as if your work was started from the latest main commit.

• First pull the latest changes of main branch.
• Then navigate to the working branch
• run the command git rebase main
• if there any conflicts resolve and continue rebase.
• After rebasing completely, force push the changes.
#git

Published: Oct 29, 2024
Author: Nitturu Baba
System Analyst

To avoid N+1 queries in Rails, you can use the .includes method to eager-load associated records, which reduces the number of database calls.

Suppose you have two models: Order and Item, where an Order has many Items. Without eager-loading, querying each order’s items individually would lead to N+1 queries.

Code

orders = Order.all 
orders.each do |order| 
  puts order.items # Each order triggers a separate query for items
end

By using .includes, Rails will fetch all associated items in a single additional query:

Code

orders = Order.includes(:items)
orders.each do |order|
  puts order.items # No extra query is triggered here
end

This approach loads Order records in one query and then fetches all associated items in a second query, avoiding the N+1 issue.

#CU6U0R822

Published: Oct 28, 2024
Author: Nitturu Baba
System Analyst

before_action runs a specified method before the controller action. It’s useful for tasks that need to happen before executing the main action, such as authentication, setting up a resource, or ensuring permissions.

after_action runs a specified method after the controller action has executed. It’s useful for tasks that need to happen after the response is rendered, such as logging activity, tracking metrics, or cleaning up resources.

Code

class PointsController < ApplicationController
  before_action :set_user_points, only: [:show, :redeem]
  after_action :update_points_history, only: [:redeem]

  def show
    # Show points balance
  end

  def redeem
    # Redeem points logic
  end

  private

  def set_user_points
    @points = current_user.points
  end

  def update_points_history
    # Log the points redemption action
  end
end

In the above example set_user_points will execute before the controller actions show and redeem. update_points_history will execute after the redeem action.

#CU6U0R822

Published: Oct 25, 2024
Author: Ayasha Pandey
System Analyst

onDelete: Cascade in Prisma automatically deletes the child records when a parent record is deleted.

Code

model User {
  id    Int     @id @default(autoincrement())
  posts Post[]
}

model Post {
  id     Int   @id @default(autoincrement())
  userId Int
  user   User  @relation(fields: [userId], references: [id], onDelete: Cascade)
}

Now when you delete a user:

Code

await prisma.user.delete({ where: { id: 123 } })

All their posts are automatically deleted too!

#prisma #schema

Published: Oct 25, 2024
Author: Nived Hari
System Analyst

Combining Commits with Git Squash
Squashing commits allows us to combine multiple related commits into a single one, helping to keep the commit history clean.

Let's say if we want to combine 3 separate commits which are related to same thing into one clean commit,

1. Checkout the branch

Code

git checkout branch-name

2. Run the following command

Code

git rebase -i HEAD~3

3. Modify the rebase file. Git will open a text window with last 3 commits

Code

pick 7f9d4bf first commit
pick 3f8e810 second commit
pick ec48d74 third commit

• pick means to keep the commit as is.
• To squash the second and third commits into the first one, change pick to squash / s for those commits.
4. After we save and exit, another text editor will pop-up with commit messages

Code

# This is a combination of 3 commits.
# The first commit message:

fix for bug

# Commit message for #2:
Updated this

# Commit message for #3:
Added comments & updated README

Simply saving this will result in a single commit with a commit message that is a concatination of all 3 messages.
We can choose which one we want, or we can create a new message entirely.
5. Complete the Rebase
After saving, we now have a single commit representing the previous three.

#git #rebase

Published: Oct 24, 2024
Author: Nived Hari
System Analyst

Concerns
A Rails concern is just a plain Ruby module that extends the ActiveSupport::Concern module provided by Rails.
They help in organizing and reusing code across controllers and models by extracting common functionality into modules.

There are 2 main blocks in a concern

1. included

1. Any code inside this block is evaluated in the context of the including class.
2. if sample class includes a concern, anything inside the included block will be evaluated as if it was written inside the sample class.
3. This block can be used to define Rails macros like validations, associations, and scopes.
4. Any method you create here becomes instance methods of the including class.
2. class_methods

1. Any methods that you add here become class methods on the including class.
Example:

typically concerns are located in app/controllers/concerns or app/models/concerns

Code

module ExampleConcern
  extend ActiveSupport::Concern

  included do
    # any code that you want inside the class
    # that includes this concern
  end

  class_methods do
    # methods that you want to create as
    # class methods on the including class
  end
end

Including this concern in a controller:

Code

class SomeController < ApplicationController
 include ExampleConcern
end

#RubyOnRails #concerns #CU6U0R822

Published: Oct 23, 2024
Author: Adithya Hebbar
System Analyst

Here is how to generate robots.txt in Next.Js - App Router. Add a robots.js or robots.ts file in your app directory

Code

import type { MetadataRoute } from 'next'
 
export default function robots(): MetadataRoute.Robots {
  return {
    rules: {
      userAgent: '*',
      allow: '/',
      disallow: '/private/',
    },
  }
}

This will add or generate a robots.txt file that matches the https://en.wikipedia.org/wiki/Robots.txt#Standard|Robots Exclusion Standard in the root of app directory to tell search engine crawlers which URLs they can access on your site.

#js #nextjs #seo

Published: Oct 22, 2024
Author: Ayush Srivastava
System Analyst

We can generate a UUID in Rails using SecureRandom.uuid without needing any gem
#CU6U0R822

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