Aspect-Oriented Programming (AOP) is a programming paradigm focused on modularizing cross-cutting concerns—aspects of a program that affect multiple parts of the codebase and don't fit neatly into object-oriented or functional structures.
Typical cross-cutting concerns include logging, security checks, error handling, transaction management, or performance monitoring. These concerns often appear in many classes and methods. AOP allows you to write such logic once and have it automatically applied where needed.
Aspect: A module that encapsulates a cross-cutting concern.
Advice: The actual code to be executed (e.g., before, after, or around a method call).
Join Point: A point in the program flow where an aspect can be applied (e.g., method execution).
Pointcut: A rule that defines which join points are affected (e.g., "all methods in class X").
Weaving: The process of combining aspects with the main program code—at compile-time, load-time, or runtime.
@Aspect
public class LoggingAspect {
@Before("execution(* com.example.service.*.*(..))")
public void logBeforeMethod(JoinPoint joinPoint) {
System.out.println("Calling method: " + joinPoint.getSignature().getName());
}
}
This code automatically logs a message before any method in the com.example.service
package is executed.
Improved modularity
Reduced code duplication
Clear separation of business logic and system-level concerns
Can reduce readability (the flow isn't always obvious)
Debugging can become more complex
Often depends on specific frameworks (e.g., Spring, AspectJ)
Assertions are programming constructs used to check assumptions about the state of a program. An assertion tests whether a specific condition is true—if it isn't, an error is typically raised and the program stops.
x = 10
assert x > 0 # passes
assert x < 5 # raises AssertionError, since x is not less than 5
They help with debugging: you can verify that certain conditions in code hold true during development.
They document implicit assumptions, e.g., “At this point, the list must have at least one item.”
They are mainly used during development—assertions are often disabled in production code.
Assertions are meant to catch programmer errors, not user input or external failures. For example:
assert age > 0
→ inappropriate if age
comes from user input.
Instead, use: if age <= 0: raise ValueError("Age must be positive.")
Design by Contract (DbC) is a concept in software development introduced by Bertrand Meyer. It describes a method to ensure the correctness and reliability of software by defining clear "contracts" between different components (e.g., methods, classes).
In DbC, every software component is treated as a contract party with certain obligations and guarantees:
Preconditions
Conditions that must be true before a method or function can execute correctly.
→ Responsibility of the caller.
Postconditions
Conditions that must be true after the execution of a method or function.
→ Responsibility of the method/function.
Invariant (Class Invariant)
Conditions that must always remain true throughout the lifetime of an object.
→ Responsibility of both the method and the caller.
Clear specification of responsibilities.
More robust and testable software.
Errors are detected early (e.g., through contract violations).
class BankAccount {
private double balance;
// Invariant: balance >= 0
void withdraw(double amount) {
// Precondition: amount > 0 && amount <= balance
if (amount <= 0 || amount > balance) throw new IllegalArgumentException();
balance -= amount;
// Postcondition: balance has been reduced by amount
}
}
Clear contracts reduce misunderstandings.
Easier debugging, as violations are detected immediately.
Supports defensive programming.
Requires extra effort to define contracts.
Not directly supported by all programming languages (e.g., Java and C++ via assertions, Python with decorators; Eiffel supports DbC natively).
Perl Compatible Regular Expressions (PCRE) are a type of regular expression syntax and engine that follows the powerful and flexible style of the Perl programming language. They offer advanced features that go beyond the basic regular expressions found in many older systems.
Perl was one of the first languages to introduce highly expressive regular expressions. The PCRE library was created to bring those capabilities to other programming languages and tools, including:
Python (similar via the re
module)
JavaScript (with slight differences)
pcregrep
(a grep version supporting PCRE)
Editors like VS Code, Sublime Text, etc.
✅ Lookahead & Lookbehind:
(?=...)
– positive lookahead
(?!...)
– negative lookahead
(?<=...)
– positive lookbehind
(?<!...)
– negative lookbehind
✅ Non-greedy quantifiers:
*?
, +?
, ??
, {m,n}?
✅ Named capturing groups:
(?P<name>...)
or (?<name>...)
✅ Unicode support:
\p{L}
matches any kind of letter in any language
✅ Assertions and anchors:
\b
, \B
, \A
, \Z
, \z
✅ Inline modifiers:
(?i)
for case-insensitive
(?m)
for multiline matching, etc.
(?<=\buser\s)\w+
This expression matches any word that follows "user " using a lookbehind assertion.
PCRE are like the "advanced edition" of regular expressions — highly powerful, widely used, and very flexible. If you're working in an environment that supports PCRE, you can take advantage of rich pattern matching features inspired by Perl.
In software development, a guard (also known as a guard clause or guard statement) is a protective condition used at the beginning of a function or method to ensure that certain criteria are met before continuing execution.
A guard is like a bouncer at a club—it only lets valid input or states through and exits early if something is off.
def divide(a, b):
if b == 0:
return "Division by zero is not allowed" # Guard clause
return a / b
This guard prevents the function from attempting to divide by zero.
Early exit on invalid conditions
Improved readability by avoiding deeply nested if-else structures
Cleaner code flow, as the "happy path" (normal execution) isn’t cluttered by edge cases
function login(user) {
if (!user) return; // Guard clause
// Continue with login logic
}
Swift (even has a dedicated guard
keyword):
func greet(person: String?) {
guard let name = person else {
print("No name provided")
return
}
print("Hello, \(name)!")
}
Vite is a modern build tool and development server for web applications, created by Evan You, the creator of Vue.js. It is designed to make the development and build processes faster and more efficient. The name "Vite" comes from the French word for "fast," reflecting the primary goal of the tool: a lightning-fast development environment.
The main features of Vite are:
Fast Development Server: Vite uses modern ES modules (ESM), providing an ultra-fast development server. It only loads the latest module, making the initial startup much faster than traditional bundlers.
Hot Module Replacement (HMR): HMR works extremely fast by updating only the changed modules, without needing to reload the entire application.
Modern Build System: Vite uses Rollup under the hood to bundle the final production build, enabling optimized and efficient builds.
Zero Configuration: Vite is very user-friendly and doesn’t require extensive configuration. It works immediately with the default settings, supporting many common web technologies out-of-the-box (e.g., Vue.js, React, TypeScript, CSS preprocessors, etc.).
Optimized Production: For production builds, Rollup is used, which is known for creating efficient and optimized bundles.
Vite is mainly aimed at modern web applications and is particularly popular with developers working with frameworks like Vue, React, or Svelte.
Salesforce Apex is an object-oriented programming language specifically designed for the Salesforce platform. It is similar to Java and is primarily used to implement custom business logic, automation, and integrations within Salesforce.
Cloud-based: Runs exclusively on Salesforce servers.
Java-like Syntax: If you know Java, you can learn Apex quickly.
Tightly Integrated with Salesforce Database (SOQL & SOSL): Enables direct data queries and manipulations.
Event-driven: Often executed through Salesforce triggers (e.g., record changes).
Governor Limits: Salesforce imposes limits (e.g., maximum SOQL queries per transaction) to maintain platform performance.
Triggers: Automate actions when records change.
Batch Processing: Handle large data sets in background jobs.
Web Services & API Integrations: Communicate with external systems.
Custom Controllers for Visualforce & Lightning: Control user interfaces.
Memcached is a distributed in-memory caching system commonly used to speed up web applications. It temporarily stores frequently requested data in RAM to avoid expensive database queries or API calls.
Key-Value Store: Data is stored as key-value pairs.
In-Memory: Runs entirely in RAM, making it extremely fast.
Distributed: Supports multiple servers (clusters) to distribute load.
Simple API: Provides basic operations like set
, get
, and delete
.
Eviction Policy: Uses LRU (Least Recently Used) to remove old data when memory is full.
Caching Database Queries: Reduces load on databases like MySQL or PostgreSQL.
Session Management: Stores user sessions in scalable web applications.
Temporary Data Storage: Useful for API rate limiting or short-lived data caching.
Memcached: Faster for simple key-value caching, scales well horizontally.
Redis: Offers more features like persistence, lists, hashes, sets, and pub/sub messaging.
sudo apt update && sudo apt install memcached
sudo systemctl start memcached
It can be used with PHP or Python via appropriate libraries.
The Whoops PHP library is a powerful and user-friendly error handling tool for PHP applications. It provides clear and well-structured error pages, making it easier to debug and fix issues.
✅ Beautiful, interactive error pages
✅ Detailed stack traces with code previews
✅ Easy integration into existing PHP projects
✅ Support for various frameworks (Laravel, Symfony, Slim, etc.)
✅ Customizable with custom handlers and loggers
You can install Whoops using Composer:
composer require filp/whoops
Here's a simple example of how to enable Whoops in your PHP project:
require 'vendor/autoload.php';
use Whoops\Run;
use Whoops\Handler\PrettyPageHandler;
$whoops = new Run();
$whoops->pushHandler(new PrettyPageHandler());
$whoops->register();
// Trigger an error (e.g., calling an undefined variable)
echo $undefinedVariable;
If an error occurs, Whoops will display a clear and visually appealing debug page.
You can extend Whoops by adding custom error handling, for example:
use Whoops\Handler\CallbackHandler;
$whoops->pushHandler(new CallbackHandler(function ($exception, $inspector, $run) {
error_log($exception->getMessage());
}));
This version logs errors to a file instead of displaying them.
Whoops is mainly used in development environments to quickly detect and fix errors. However, in production environments, it should be disabled or replaced with a custom error page.
Swift is a powerful and user-friendly programming language developed by Apple for building apps on iOS, macOS, watchOS, and tvOS. It was introduced in 2014 as a modern alternative to Objective-C, designed for speed, safety, and simplicity.
Swift is primarily used for Apple platforms but can also be utilized for server-side applications and even Android or Windows apps in some cases.