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Ruby Tutorial Series Setup and Variables

Authors

In this post we will setup our Ruby environment, then start printing out values to the console and will also be touching on variables.

Ruby Environment:

I have a Docker image built on Alpine, the resources can be found via:

To setup a Ruby environment on your workstation, I would recommend using https://github.com/rbenv/rbenv.

Drop into a Ruby Shell:

I will be using Docker to drop into a ruby container:

$ docker run -it rbekker87/alpine-ruby:2.5 sh

       ______       _____
______ ___  /__________(_)___________
_  __ `/_  /___  __ \_  /__  __ \  _ \
/ /_/ /_  / __  /_/ /  / _  / / /  __/
\__,_/ /_/  _  .___//_/  /_/ /_/\___/
            /_/

Alpine Build:
Container Hostname: 8a4dfc590dd0
Checkout my Docker Blogs:
- https://sysadmins.co.za/tag/docker
- http://ruan.dev/tags/docker

$ irb
irb(main):001:0>

If you have the irb output, you should be good to go.

Strings and Integers

You will find when you enter a string, which is represented as one or more characters enclosed within quotation marks:

irb(main):001:0> "hello"
=> "hello"

The integers will be without the quotation marks, when we introduce anything within quotation marks, ruby will read it as a string. So for a integer, lets provide ruby with a number and the number will be returned to the shell:

irb(main):002:0> 1
=> 1

Using mathematical symbols like the + will either sum the two values when they are integers, or concatenate when they are strings.

Let's start with strings: we will add the string hello and world

irb(main):003:0> "hello" + "world"
=> "helloworld"

Now let's add two numbers together, 10 and 20:

irb(main):004:0> 10 + 20
=> 30

As you can see, it did a calculation on the two numbers as they were treated as integeres. But what happens when we add them as strings?

irb(main):005:0> "10" + "20"
=> "1020"

Adding them as strings, will concatenate them.

String Methods

Ruby's strings has many built in methods, which makes it convenient manipulating data, let me go through a couple that I am working with:

Getting the length of the string:

irb(main):006:0> "hello".length
5

Is the string empty?

irb(main):007:0> "hello".empty?
=> false

Getting the index position of 0 of the string:

irb(main):008:0> "hello"[0]
=> "h"

Getting a array of your string:

irb(main):009:0> "hello".chars
=> ["h", "e", "l", "l", "o"]

Returning your string in Uppercase:

irb(main):010:0> "hello".upcase
=> "HELLO"

Returning your string in Lowercase:

irb(main):011:0> "HELLO".downcase
=> "hello"

Capitalize your String:

irb(main):012:0> "hello".capitalize
=> "Hello"

Swap the case of your string:

irb(main):013:0> "Hello".swapcase
=> "hELLO"

Variables

Let's define variables to the static content that we used above.

Let's define our key: word to the value: of hello, world:

irb(main):019:0> word = "hello, world"
=> "hello, world"

Accessing the variables value:

irb(main):020:0> word
=> "hello, world"

We can also use puts, which stands for put string, which prints out the value to the terminal:

irb(main):021:0> puts word
hello, world

We can also, format our variable so that we can add something like a exclamation mark:

irb(main):022:0> puts "#{word}!"
hello, world!

Let's do the same with integers:

irb(main):023:0> num_1 = 10
=> 10
irb(main):024:0> num_2 = 20
=> 20

Now when we calculate the numbers using variables, you will find the expected result of 30:

irb(main):025:0> num_1 + num_2
=> 30

or:

irb(main):026:0> num_1 + num_2
puts "#{num_1 + num_2}"
30

Variables are Mutable:

Remember that variables are mutable, so they can be changed after they have been set, lets take age for example:

irb(main):027:0> age = 20
irb(main):028:0> puts age
20

irb(main):029:0> age = 22
irb(main):030:0> puts age
22

Strings and Integers:

What happens when we add strings and integers together in one line:

irb(main):038:0> name = "ruan"
=> "ruan"
irb(main):039:0> id = 120398
=> 120398
irb(main):040:0> puts "#{name + id}"
Traceback (most recent call last):
        3: from /usr/bin/irb:11:in `<main>'
        2: from (irb):40
        1: from (irb):40:in `+'
TypeError (no implicit conversion of Integer into String)

That is because we cant concatenate strings with integers, so we will need to convert the integer to a string, we do that with the to_s method:

irb(main):041:0> puts "#{name + id.to_s}"
ruan120398

And if we want to define that to a variable:

irb(main):042:0> userid = "#{name + id.to_s}"
irb(main):043:0> userid
=> "ruan120398"

Working with rb files:

We can add this together in a file with a .rb extension and call the file as an argument with ruby, as a script:

Create the file, in my case test.rb

$ vim test.rb

user = "ruan"
idnumber = 23049823
userid = "#{user + idnumber}"

puts "#{userid}"

Running the ruby file:

$ ruby test.rb
ruan23049823

Resources:

Thank You

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