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: May 8, 2024
Author: Giritharan
System Analyst

Classes And Functions in Ts.
Classes:
• Ts add helps to add type annotations for the classes.

Code

class User {
  constructor(public name: string, public age: number) {}
}
const ue = new User("github", 24);

• In Ts we don't need to initialize the properties and values inside the constructor if we are using access modifiers in the params. TypeScript will automatically initialise and assign values to class properties.
Getters / Setters:
• Classes can also have accessors
• For the getter function we can able to set return value type but for setter function we can't.
• setter functions are always expected props.
• If a getter exists but no setter the property is automatically readonly
• If the type of the setter parameter is not specified, it is inferred from the return type of the getter
• For class props always try to use _ name convention for better maintainbility.

Code

class User {
  private _currentCount: number = 0;
  constructor(public name: string, public age: number) {}

  get fetch_name(): string {
    return this._name;
  }

  get fetchCount(): number {
    return this._currentCount;
  }

  set increaseCount(prop: number) {
    this._currentCount = prop + this._currentCount;
    this.logData();
  }

  private logData(): void {
    console.log("Count Increased");
  }
}

const fetchUser = new User("github", 24);

Abstract:
• If classes or method are marked as abstract those are only for readonly purposes, means they can be only used as base class/sub class.
• So that reason we can't create object on the class who are marked as abstract.

Code

abstract class Photo {
  constructor(public isCameraOn: boolean, public isFlashOn: boolean) {}
}

class Phone extends Photo {}
const ph = new Phone(true, true);

#typescript #javascript

Published: May 7, 2024
Author: Giritharan
System Analyst

Typescript Learning

Variable definition:
In Typescript we can specify the type string, number and boolean like

Code

let myName: string = "Vijay";
    let age: number = 20;
    let isActive: boolean = false;

Moreover, if we don't specify the type typescript automatically detects the type by itself. But end of the defining the type was a good convention.

Function Definition:
• For defining a function we can specify the function parameters type. Along with that we can able to set the default value. And also the return value.

Code

function sum(a: number, b: number = 2): number {
        return a + b;
    }

• For Arrow function:

Code

let sum = (a: number, b: number = 2): number => a + b;

Why don't use any :
• Using any in TypeScript bypasses type checking but undermines TypeScript's static typing advantages. It's better to specify types explicitly for safer and more maintainable code.
Array:
With the help of the array, we can store number, string and boolean values separately and mixed.

Code

For String
 let users: string[] = ["a", "b", "c", "d]

For Number
 let count: number[] = [1, 2, 3, 4]

For boolean
let isActive: boolean[] = [true, false]

For Mixed array
 let allDate: (string | number)[] = ["a", "b", "c", 1]
 Here Array contains only integers and strings

Void And Never:
• void is a type that represents the absence of returning value. It's often used as the return type of function that doesn't return any value.

Code

function logError(msg: string): void {
    console.log(msg);
}

• never represents the type of values that never occur:. It's typically used as the return type of functions that never return (i.e., always throw an error).

Code

function throwError(message: string): never {
    throw new Error(message);
}

Object Type:
• Object Types is used to pass the object as a parameter in the functions.

Code

function fetchData(pt: { x: number; y: number }) {
  return pt;
}
fetchData({ x: 3, y: 7 });

• If we want mentioned as an optional prop we can do that with the help of ? operator

Code

function fetchData(pt: { x: number; y?: number }) {
  return pt;
}
fetchData({ x: 3 });

Union Types:
• It means type can be formed in two or more types, which means values can be anything from the union value.

Code

function sum(a: string | number) {
        return a;
    }
Here you can see value can be anything string or number

Type Aliases
• When can use both object type and union type but if we want use more than once we can use Type Aliases or Interface .

Code

type User = {
  name: string;
  age: number;
}

function displayUser(prop: User) {
  console.log(prop.name);
  console.log(prop.age);
}

displayUser({name: 'John', age: 22})

• Moreover on the type, we can able to do extend the values.

Code

type User = {
  name: string;
  age: number;
}

type Role = {
  role: string
}

type UserDeatils = User & Role & {
  address: string;
}

• From above you can see that the userDetails inherits the user and role props without adding extra value. So that helps to keep DRY over time.
Interface:
• Interface is also similar in concept to type._ it's another way to name an object type.

Code
interface User { name: string; age: number; } function displayUser(prop: User) { console.log(prop.name); console.log(prop.age); } displayUser({name: 'John', age: 22})

• It allows the extending feature.

Code
interface User { name: string; age: number; } interface Role { role: string } interface userDetails extends User, Role { address: string; }

• The Only difference is type not available for re-opening for adding new properties.
Readonly and Optional:
• with the help of that, we can mark the value as read-only or optional.

Code
type User = { readonly id: string; name: string; phone: number; isActive: boolean; email?: string; };

• If we try to access id typescript will throw an exception. Also, email is not present on obj it does not make exceptions.
Tuples:
• Tuples are a data structure that allows you to store a fixed-size, ordered collection of elements.
• Each element in a tuple may have a different data type. They are similar to arrays, but their size and types are fixed once they are defined.

Code
let myTuple: [string, number, boolean]; myTuple = ['hello', 10, true];

• In typles we can modify elements of the tuple using array method with different types. It doesn't show any warning we always need to be aware of it.
Enums:
• Enums in TypeScript are usually _used to represent a determined number of options for a given value.
• TypeScript provides both numeric and string-based enums
• Numeric enums:
▪︎ By default enum value starts from 0 until we explicitly mention something:

Code

const enum UserType {
  ADMIN,
  USER,
  GUEST,
}

• We can explicitly change the enum value

Code

const enum UserType {
  ADMIN = 10,
  USER,
  GUEST,
}

• so from now value goes like 11, 12 in upstream
• String enums:
◦ String enums are similar to numbers, But here we can specify string instead of numeric

Code

const enum UserType {
  ADMIN = "admin",
  USER = "user",
  GUEST = "guest",
}

• Heterogeneous enums:
◦ We can mix up string and numeric on enum. But After string, if numeric get started we need to mention the numeric value for the first one.

Code

const enum UserType {
  ADMIN = "admin",
  USER = 0,
  GUEST,
}

• Remaining value can typescript will handles.
#typescript #javascript

Published: May 7, 2024
Author: Syed Sibtain
System Analyst

In Rails, a partial is a reusable view template that allows you to encapsulate a portion of a view into a separate file. Partials are useful for organising and reusing code, especially when certain components or elements are repeated across multiple views within an application.

We can create a partial by creating a new file with a name that begins with an underscore (_). For example, _sidebar.html.erb or _header.html.erb.

And to render a partial within another view, use the render method with the name of the partial file (without the underscore) as an argument. For example, <%= render 'sidebar' %> will render the _sidebar.html.erb partial within the current view.

#rails

Published: May 2, 2024
Author: Syed Sibtain
System Analyst

The rails routes command generates a comprehensive list of all routes defined in our Rails application, displaying the HTTP method, URL pattern, controller, and action associated with each route.

#rails

Published: Apr 29, 2024
Author: Satya

find your rails code smells by using a gem called flog . Flog finds the most tortured code in your codebase.

Code

gem install flog

then run

Code

flog app lib

it will print the flog score for the all files that has score more than or equal to 10. Generally we should make sure flog score should be less than 10.
Note: The more the flog score , the more pain the code is in.
#rails #code-smells #flog

Published: Apr 26, 2024
Author: Syed Sibtain
System Analyst

In Ruby, instance variables are variables that belong to a specific instance of a class. They are prefixed with the @ symbol and are accessible within the instance methods of that class. Instance variables allow objects to maintain state and store information unique to each instance.
Example:

Code

class Person
  def initialize(name, age)
    @name = name
    @age = age
  end

  def say_intro
    puts "Hello, my name is #{@name} and I am #{@age} years old"
  end
end

# Create a new instance of Person
person1 = Person.new("John", 18)

# Call the say_intro method
person1.say_intro

In this example, @name is an instance variable of the Person class, representing the name of each Person object created. The initialize method is a constructor that sets the value of @name when a new Person object is created. The say_intro method uses the instance variable @name to give the intro of the person with their name and age when called.

#ruby

Published: Apr 25, 2024
Author: Nisanth

The docker stats command is a powerful tool provided by Docker to monitor the resource usage of running containers. It provides a real-time stream of various metrics such as CPU usage, memory usage, network I/O, block I/O, and the number of processes (PIDs) running inside each container. This command is particularly useful for performance analysis and ensuring that containers are running within their resource limits.
Example Explanation

Code

docker stats db370fc6b784
CONTAINER ID   NAME       CPU %     MEM USAGE / LIMIT     MEM %     NET I/O          BLOCK I/O       PIDS
db370fc6b784   minikube   43.70%    1.243GiB / 2.148GiB   57.87%    35.4MB / 414MB

#devops #docker

Published: Apr 24, 2024
Author: Vaibhav Yadav
Senior System Analyst

We can check the default value for a given column using postgres query like this:

Code

SELECT column_name, column_default
FROM information_schema.columns
WHERE table_name = '<table_name_placeholder>' AND column_name = '<column_name_placeholder>';

Same can be used for constraints like is_nullable as following:

Code

SELECT column_name, is_nullable
FROM information_schema.columns
WHERE table_name = '<table_name_placeholder>' AND column_name = '<column_name_placeholder>';

#database #postgres #query

Published: Apr 23, 2024
Author: Sujay

active_record_doctor performs variety of health checks to identify and rectify common database issues like missing foreign key constraints, missing NON NULL constraints, missing presence validations, incorrect presence validations on boolean columns and many more. Ref: https://github.com/gregnavis/active_record_doctor
#rails #database

Published: Apr 22, 2024
Author: Sagar Ghorse

while integrating sentry with gitlab ip whitelisting needs to be done on gitlab server (self-hosted)
#devops #sentry#gitlab

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