DEV Community: José Gomes

Factory Method

José Gomes — Tue, 12 Jul 2022 09:38:11 +0000

Design patterns should not be applied indiscriminately. Often they achieve flexibility and variability by introducing additional levels of indirection, and that can complicate a design and/or cost you some performance. A design pattern should only be applied when the flexibility it affords is actually needed - Erich Gamma

Introduction

One of the biggest challenges in software development is how to write code that enables easy scalability, maintenance, and flexibility.

One solution for this problem is to use Design Pattern, a guideline of good practices to write clean and organized code, allowing anyone to easily understand and contribute.

Design Patterns can be divided into 4 categories:

Creational: Object instantiation
Structural: Class relationships and hierarchies
Behavioral: Object intercommunication

The creational categories include five methods:

Factory method
Abstract method
Builder method
Prototype method
Singleton method

Today we will focus on the Factory method!

What is Factory Method?

The factory method encapsulates the creation of related objects, providing an interface to create an object but defers the creation to the sub-class. This is one of the most methods used, the reason for that are the benefits:

Creates objects based on runtime parameters
Do not need to know which objects you will need
Lets the subclasses instantiate the object instead of the min
Easily add new products or change existing ones
No need to make changes throughout
Extensible to include objects
Object generation located in one place
Easily switch between factories

Structure

In the factory method, we have three structures:

Class creator: Provide some default implementation of the factory method.
Concrete creator: Override the factory method in order to change the resulting product's type.
Concrete product: Provides various implementation of the product interface.

Pratice

Here we will learn how to use a Factory Method, through a very simple example of a game, where we must spawn different types of rock, in the first moment, we will have two types of rock: Small and Mid. The way the code is written will be very easy to register a new type of rock(E.g: Big, Iron).

#include <iostream>

using namespace std;

//Class creator
class rock {
public:
    rock(){}
    char *getType(){
        return _type;
    }
};

//Concrete product
class smallRock:public rock{
public:
    smallRock(){
        //_type = "Small";
        cout << "\nSmall rock created" << endl;
    }
};

//Concrete product
class midRock:public rock{
public:
    midRock(){
        //_type = "mid";
        cout<<"\nMid rock created" << endl;
    }
};

/*Creator concrete*/ 
class rockFactoryCreator{
public:
    rock *GetRock(){
        int choice;
        cout << "Select type of rock to make: " << endl;
        cout << "1: Small" << endl;
        cout << "2: Mid" << endl;
        cout << "Selection: ";
        cin >> choice;

        switch (choice)
        {
        case 1:
            return new smallRock;
        case 2:
            return new midRock;
        default:
            cout << "Invalid Selection" << endl;
            return NULL;
        }  
    }
};

int main()
{
    rockFactoryCreator rockCreator;
    rock *asteroid; 
    asteroid = rockCreator.GetRock();
    system("PAUSE");
    return 0;
}

Introduction to Embedded Systems

José Gomes — Wed, 27 Apr 2022 19:10:45 +0000

Nowadays embedded systems are everywhere, in cars, mobile phones, home appliances, medical centers and even in space! The first known embedded device was the Apollo Guidance Computer, developed in the 1960s by Dr. Charles Stark Draper at the Massachusetts Institute of Technology for the Apollo Program. Markets and Markets predict that in 2025 the embedded market size is expected to reach USD 116.2 billion by 2025! It is time to start to understand the amazing world of embedded development.

What is Embedded Systems ?
An embedded system is a microprocessor or microcontroller-based system of hardware and software designed to perform specific purposes and can be classified as:

Subsystems

Part of a large system
Independently is useless

Stand-Alone Systems

Can perform its functions independently
Components and techniques used to build these belong to the same class as the “subsystems class of embedded systems and hence are viewed as embedded systems too

Network system

A group of physically separate electronic devices that perform a collective function

Architecture

Embedded systems can be composed of many hardware components, such as sensors, A-D converters, and actuators. But in almost every embedded system these components are presented:

Microprocessor
Ram
Flash memory
Serial Transversos

Important Technologies

If you are interested in start in this area, here are some of the technologies that can help you in this process:

C/C++
Java
Rust
Assembly
Electronics
FPGA
Arduino
Data Structure and Algorithms

References
https://www.marketsandmarkets.com/Market-Reports/embedded-system-market-98154672.html
https://dev.to/ahmedmansoor012/what-are-embedded-systems-44f0

IAM & EC2

José Gomes — Thu, 14 Apr 2022 20:08:03 +0000

IAM and EC2 are two of the most basic services you need to know to control and use AWS technologies.

First of all, it is important to understand Regions and Availability!

Regions and Availability Zones

All services in AWS, except IAM and S3, are separated per region, which is a physical location around the world that is a cluster of Availability Zone(Data Center). One important thing to know is that Regions and Availability Zones(AZ) are identified by numbers and letters. Regions are finished by numbers and AZ is finished by letters.

IAM - Identity & Access Management

When we start to talk about IAM, one of the most important things to know is about Policy, which defines what is allowed and what is not allowed.

Policies can be associated with Users, Groups, or specific roles. AWS provides a lot of predefined policies but is possible to create a new one with specific assignments.

For companies that already have a set of credentials, it is possible to use the IAM Federation that connects the Active Directory with IAM.

EC2 - Elastic Compute Cloud

EC2 allows the user to create an instance allocated in one AZ. Through EC2 you don't need to worry about hardware anymore. In each instance, the user can configure the CPU, Memory, Regions, and AZ. There are a few functionalities very interesting, such as:

EC2: Rent of virtual machines
EBS: Storage of data in virtual disks
ELB: Distribution of traffic between virtual machines
ASG: Autoscaling
AWS provides some pre-configured instances, known as Amazon Machine Images(AMIs).

EC2::Security Group
To launch an instance you need to configure the security group that defines if the data can reach the instance or not.

Security groups work as a firewall, any data attended to the instance is intercepted by the security group and inf the source is allowed, the data can continue the route to the instance.

Important to know:

Can be associated with many instances
All the data is intercepted before reaches the instance
For standard: All input data is blocked
For standard: All output data is allowed

EC2::Elastic IP

When we stop an EC2 instance the public IP can change. This can cause problems. To have a static public IP is necessary to use Elastic IP.

Important to know:

It is not indicated to use Elastic IP for production. Indicates a low-quality architecture solution.
Indicated use of Load Balance
Can be associated with one instance at a time

EC2::User Data

When you launch an instance for the first time, you may want to prepare a basic environment by updating packages, downloading files from the internet, or installing some applications. This is possible by using User Data in a specific area where you can write the command and when the instance is launched for the first time, the commands will be executed.

Important to know:

The commands are executed as admin
The commands are executed only one time(When you launch for the first time)

EC2::Types of Intances

On Demand:

Short-time projects
Pays only for what is used
High Cost
Without contract, you can finish in any moment
Indicated only for development

Reserved:

Long-time project
Payment in advance
Reservation for 1 to 3 years
Stable applications

Spot:

Short-time projects
Very cheap
Work as a public sale, if you win, you will have the right to use the instance until someone pay more
If someone pay more, aws only gives 2 minutes and them the instance will be finished
Indicated for projects that accept interruptions

Dedicated:

A dedicated hardware
Can share instances with other that own the same account
No placehold control ( If you shutdown the instance the hardware can change)

Dedicated Host:

Dedicated Hardware
Control of placement
Access to hardware configuration
Very expesinve

Thank you for reading. Happy Cloud Computing!