WTF is S.O.L.I.D – WTF is S ?

In this series I am going to be going through each of the principles. Go about explaining them in as simple of a manner as possible.

S = Single Responsibility Principle

Anything inside your code that is parts (class, modules, etc) should only ever have one reason to change. For example if you had a Person class, then everything in that class should only do things related to person. A person class should have methods like “eat”, “sleep”, “play”, and etc. However a person should never need to have a “log” method, cause it has nothing to do with a person.

 

4 Reasons why you should choose React for your next project !

1) Don’t Touch the DOM – Imperative Vs Declarative

Hey don’t touch the DOM ! React will do that for you. You might be wondering what I mean by that. You see React shields you from manually interacting (Imperative)  with the DOM using Java Script. Instead React uses something called the “Virtual DOM”. The Virtual DOM is a representation of the actual DOM that React uses to figure out what to actually change on the screen. React will always be like “Oh you made that change ? Let me handle the best way that update“. So when you use React you are using a Declarative way of programming.

2) Hair Balls Vs Lego – Component Architecture

Front end Apps these days are pretty complex, for example take Netflix, Facebook, or AirBnB. They all have complex user interactions and require a large number of cross interacting entities. If you tried to build any one of these applications using vanilla Java-script, and then tried to add more and more features to them, you would end up with a large hair ball of code. That would feature large chunks of CSS, JS, and HTML all over the place. And when anyone ever tried to add a new feature, they would have to copy and past code (the horror !). Components to the rescue ! With components you can encapsulated each and every aspect of your app into little manageable chunks, that can be imported into other parts of your application. Making building new features as easy as building with Lego.

3) One Way Data Flow

Every application has “State“. This can be anything from how many times you clicked a button, to your current permissions inside the app. Now in traditional front end apps this state is spread around different chunks of the app. And are not shareable across different areas of the app. For example if you had a news editor app, it would have to know who has permissions to actually publish the content, and give the user some categories to publish it under.

React deals with this problem by enforcing a centralized state. Once the “State” of the app changes, React automatically reacts and makes the necessary DOM changes to reflect the change. With this centralization you minimize the places where potential bugs show up. And you have a better idea where the bugs are in your application. Since data only flows one through your application, from your “State” to the components.

4) Just the UI

React is a library for building UIs, plain and simple. It does not try to be a large massive framework that has every single feature you could want. Therefor you can just add the extra features you want as third party libraries. This way your app becomes highly customized towards your use, rather than you needing to bend a framework to work the way you want it too.

 

Why you should get started on that side project now !

All programmers ( code carpenters, developers, software engineers, or what ever you like to go by) should constantly be making things, on the side, for free.

Why would anyone do something for free, when they could get paid for it ? Well what if I said that it could lead to more money down the line ? Would you do it ? And if you did do it, would you only do it for the money ?

Now if you became something for purely the purposes of making money, then …. well …. you are probably gonna have a pretty unfulfilling life, full of big houses, and fancy cars … maybe. However I think people should do things because it satisfies them. Doing something that satisfies you feeds you “soul” .

As a code carpenter I make things for a living, that help people out. And in general I like making things in any medium. So I frequently go out of my way to make alot of things, that kind of sort of have a purpose. By doing this I get a better understanding of different things, and develop experiences that will help me build things in the future.

 

WTF is Bubble Sort ?

Bubble sort is a type of sorting algorithm. Its not the best for everything but it does have its uses. It gets its name since it makes the largest values “bubble” to the top. Bubble sort does its job by using pair comparisons. So it takes the current value and compares it to it’s neighbor directly to the right.

Below you can see what I mean. We first take 5 and compare it 3, then ask the question “is 5 greater then 3 ? ” Then if it is, 5 switches places with 3 and if it isn’t then they stay in the same place, and move on to the next value.

BubbleSortEx1

Here you can see a non optimized implementation of it:

 

Questions People have Asked Me – Part 1

Below are some questions I was recently asked, with my answers. 

Please let me know if any of them are wrong, its a learning opportunity for me 🙂

What is the binary sort algorithm and how does it work? 

The binary sort algorithm (BSA) is used to effectively sort data. It works on the principle of continuously cutting the data set in half, until it finds what it is searching for. However, this algorithm only works on data sets that are already sorted. 

First the BSA checks the middle of the data set and compares the value it is searching for. If this value is the value it is searching for then it stops. However, if it is not equal, it checks if the value it found is bigger or smaller then the value it is trying to find. If the value is smaller, the BSA repeats the process on the left, whereas if the value is bigger it repeats the process on the right. This process is repeated multiple times until the value that the BSA is looking for is found. 

What is recursion and how is it used? 

Recursion in programming is when the program starts calling its self, from inside its self. This programming technique is usually used when a single large program can be solved in smaller parts and has a valid base case. Such as computing the Fibonacci Sequence or traversing a binary search tree. 

What is polymorphism and what is its purpose? 

Polymorphism is an aspect of Object-Oriented Programming where a “object” can take on many different forms, if all the forms are its children.  

Explain when you should use interfaces and when you should use abstract base classes. 

Both interfaces and abstract classes are a type of contract, in the class structures of a software application. Interfaces are a form of contract between two different entities, where you want to separate the functions from the implementations. This is done such that you existing application does not need to change much if a certain part of it is changed. This can be seen in the commonly used repository pattern, which is used to separate data access logic from the business logic. Where as abstract classes are a less extreme version of interfaces, where certain methods defined in it can have real implementations. This allows any child class that inherits from the abstract class to get those method implementations. The difference between the two can be further seen in how their child methods are derived. Since interfaces are “implemented”, where as abstract classes are “extended”. 

When should you use static methods and static variables? And when shouldn’t you use them. 

Static methods and variables can be used from a class without having to instantiate it. This is usually used when, you want to group a set of functionality or utility function together. An example of this is the “Math” class in JAVA, which gives the user all the math related function they need. You wouldn’t want to use them when you would be creating your inheritance-based class structures, most of the time. 

 

Write a SQL statement to create a table called “author” with the columns “id”, “name”, “age” (for MySQL or SQL Server). 

CREATE TABLE author ( 

id int NOT NULL AUTO_INCREMENT, 

name varchar(255) NOT NULL, 

age int, 

PRIMARY KEY (id) 

); 

Write a SQL statement to create a table called “book” with the columns “id”, “title”, “genre”, “author_id” (for MySQL or SQL Server). 

CREATE TABLE book ( 

id int NOT NULL AUTO_INCREMENT, 

title varchar(255) NOT NULL, 

genre varchar(255), 

author_id int, 

PRIMARY KEY (id), 

FOREIGN KEY (`author_id`) REFERENCES `author` (`id`) ON DELETE CASCADE); 

 

For the “author” and “book” tables created above, write a SQL statement to tell you the number of books each author has written, but only for authors who have written 2 or more books. The output should not show authors that have written only 1 book. The output should have the author’s name and the number of books they have written. 

SELECT author.name, COUNT(*) AS ‘# books’ FROM author, book WHERE author.id = book.author_id GROUP BY author.name HAVING COUNT(*) > 1; 

 

In databases, what are indexes used for and how to you decided how to use them effectively. 

Indexes in databases are used to speed up data retrieval. However, they come at the additional cost of space, and added complexity to database maintenance. They should only ever be used when the same type, or group of data is constantly being accessed. If the number of reads get even larger, there should also be some sort of caching layer the application queries, such that it doesn’t need to query the SQL database directly. 

 

What is the value of unit testing and what are some of your strategies for writing good unit tests? 

Unit testing is used to test the functionality of the different parts of an application. Its value lies in the fact that they make the programmer, test their code in a systematic way. And feeds into a workflow where tests are run before anything gets committed to the master branch. I think the best way to write a test case, is to write the test before writing the application logic, since it gets you thinking about what edge/special cases to consider. This is also known as the test-driven development approach. 

WTF is are Stacks, Queues, and Deques ?

Stack

A stack is a stack of books, or a stack of sandbags or a stack of elephants or even a stack of unicorns. Basically a stack is anything that follows LIFO (Last In First Out), which means that if the last thing you put onto the stack is the first thing you have to take out, then its a stack.

Lets say you build a tower of blocks, that tower is a stack. Why ? Cause to get to the block at the base you need to take off all the other blocks. Below you will see a visual example of what I am talking about.

stackexample

 

Queue

A Queue in programming is the same thing as the Queue while in line to buy food, or go to a movie, or get into a night club, its a first come first serve basis. Meaning the first thing to get out of a Queue was the first thing to go into the Queue.

You can also think of Queues as pipes that transport things. In the case of plumbing, the steel pipe and the water moving through it the Queue. Since the water that first enters the pipe is the water that first leaves the pipe.

Below is a diagram to show what I am talking about:

queuesexample

 

Deques

Deques are like the cooler older brother of the Queue, since it lets things flow in more then one direction. Now the user of the data structure can choose how they take elements out of it. If you understood how Queues worked, then you should be able to understand the diagram below.

dequesexample

A Blog With Rails

Introduction:

Warning this only works on Mac OS.

Now before you start thinking your going to make the next WordPress, let me just say we are only going to be making the MVP of a blogging site, that’s right a MVP. What is a MVP you may ask ? It stands for Minimum Viable Product, this thing we are about to build is just a web app that has CRUD functionality. What is CRUD you ask ? CRUD is Create Read Update Destroy.

Don’t be afraid of the terminal, the terminal is your friend for life 🙂 you just got to treat it right.

Up and running:

  1. Install Home Brew, is manages the software you need to manage all the software, your going to use to make software. Just follow the instructions on here: https://brew.sh/
  2. Install Bundler, it manages the specific Ruby software libraries for your application. Type the following command “gem install bundler”.
  3. Install Nokogiri, it gives Ruby the ability to understand HTML and CSS among other things. Type the following command “gem install nokogiri”. This is going to take awhile, chill out and take a break you have been working too hard 🙂
  4. Install Rails, its the thing that you build on top of, to make your web application. Ruby the language has libraries for doing different things. Rails is just a really big library for making web based applications.  As you may have guess just type in “gem install rails”.

 

Making a Rails App:

  1. CD into a folder you would like to be in and run the following command “rails new <name of your app here> -T “
  2. Now if you look into the folder you just ran this command in, you will see a folder with the name of your app. Open this with your favorite text editor, VSCode is always a good choice.
  3. CD into the newly created folder, and make your database. You can do this by running “rails db:create” and then running “rails db:migrate”. What this is doing is creating a database, and then populating it with boiler plate info.
  4. Now run “rails s” and go to the URL is gives you. You should see your app, YAY you made your first rails app 🙂 If the URL isn’t working try using http:127.0.0.1/8080 or http:127.0.0.1/3000.

 

Actually making the Blog:

  1. Run “rails g scaffold Blog title:string body:text”. What this command will do is create a Blog object, that has a title and a body and can be stored in our database. Rails knows this since “g” is for generate, “scaffold” is for create everything for me, and the rest is specify what type of things you want there to be, in the object you are creating.
  2. Now you got to let the database know about this blog object you made. To do so simply run “rails db:migrate”
  3. Finally the moment you have been waiting for, run your app with “rails s” and ta-da you go your self a working rails app 🙂