Ruby - Overview

Ruby is a pure object-oriented programming language. It was created in 1993 by Yukihiro Matsumoto of Japan.
You can find the name Yukihiro Matsumoto on the Ruby mailing list at www.ruby-lang.org. Matsumoto is also known as Matz in the Ruby community.

Ruby - Environment Setup

Try it Option Online

You really do not need to set up your own environment to start learning Ruby programming language. Reason is very simple, we already have set up Ruby Programming environment online, so that you can execute almost all the tutorial examples online at the same time when you are doing your theory work.

Ruby - Syntax

Let us write a simple program in ruby. All ruby files will have extension .rb. So, put the following source code in a test.rb file.

#!/usr/bin/ruby -w

puts "Hello, Ruby!";

Here, I assumed that you have Ruby interpreter available in /usr/bin directory. Now, try to run this program as follows:

Ruby - Classes and Objects

Ruby is a perfect Object Oriented Programming Language. The features of the object-oriented programming language include:

• Data Encapsulation:
• Data Abstraction:
• Polymorphism:
• Inheritance:
  

Ruby Variables, Constants and Literals

Variables are the memory locations which hold any data to be used by any program.
There are five types of variables supported by Ruby. You already have gone through a small description of these variables in previous chapter as well. These five types of variables are explained in this chapter.

Ruby Operators

Ruby supports a rich set of operators, as you'd expect from a modern language. Most operators are actually method calls. For example, a + b is interpreted as a.+(b), where the + method in the object referred to by variable a is called with b as its argument.
For each operator (+ - * / % ** & | ^ << >> && ||), there is a corresponding form of abbreviated assignment operator (+= -= etc.)

Ruby Comments

Comments are lines of annotation within Ruby code that are ignored at runtime. A single line comment starts with # character and they extend from # to the end of the line as follows:

#!/usr/bin/ruby -w

# This is a single line comment.

Ruby if...else, case, unless

Ruby offers conditional structures that are pretty common to modern languages. Here, we will explain all the conditional statements and modifiers available in Ruby.

Ruby if...else Statement:

Syntax:

if conditional [then]
   code...
[elsif conditional [then]
   code...]...
[else
   code...]

Ruby Loops - while, for, until, break, redo and retry

Loops in Ruby are used to execute the same block of code a specified number of times. This chapter details all the loop statements supported by Ruby.

Ruby Methods

Ruby methods are very similar to functions in any other programming language. Ruby methods are used to bundle one or more repeatable statements into a single unit.
Method names should begin with a lowercase letter. If you begin a method name with an uppercase letter, Ruby might think that it is a constant and hence can parse the call incorrectly.

Ruby Blocks

You have seen how Ruby defines methods where you can put number of statements and then you call that method. Similarly, Ruby has a concept of Block.

• A block consists of chunks of code.
• You assign a name to a block.
• The code in the block is always enclosed within braces ({}).
  

Ruby Modules and Mixins

Modules are a way of grouping together methods, classes, and constants. Modules give you two major benefits.

• Modules provide a namespace and prevent name clashes.
• Modules implement the mixin facility.
  

Ruby Strings

A String object in Ruby holds and manipulates an arbitrary sequence of one or more bytes, typically representing characters that represent human language.
The simplest string literals are enclosed in single quotes (the apostrophe character). The text within the quote marks is the value of the string:

Ruby Arrays

Ruby arrays are ordered, integer-indexed collections of any object. Each element in an array is associated with and referred to by an index.
Array indexing starts at 0, as in C or Java. A negative index is assumed relative to the end of the array --- that is, an index of -1 indicates the last element of the array, -2 is the next to last element in the array, and so on.

Ruby Hashes

A Hash is a collection of key-value pairs like this: "employee" => "salary". It is similar to an Array, except that indexing is done via arbitrary keys of any object type, not an integer index.
The order in which you traverse a hash by either key or value may seem arbitrary and will generally not be in the insertion order. If you attempt to access a hash with a key that does not exist, the method will return nil.

Date & Time in Ruby

The Time class represents dates and times in Ruby. It is a thin layer over the system date and time functionality provided by the operating system. This class may be unable on your system to represent dates before 1970 or after 2038.
This tutorial will make you familiar with all the most wanted concepts of date and time.

Ruby Ranges

Ranges occur everywhere: January to December, 0 to 9, lines 50 through 67, and so on. Ruby supports ranges and allows us to use ranges in a variety of ways:

• Ranges as Sequences
• Ranges as Conditions
• Ranges as Intervals
  

Ruby Iterators - each and collect

Iterators are nothing but methods supported by collections. Objects that store a group of data members are called collections. In Ruby, arrays and hashes can be termed collections.
Iterators return all the elements of a collection, one after the other. We will be discussing two iterators here, each and collect. Let's look at these in detail.

Ruby File I/O, Directories

Ruby provides a whole set of I/O-related methods implemented in the Kernel module. All the I/O methods are derived from the class IO.
The class IO provides all the basic methods, such as read, write, gets, puts, readline, getc, and printf.
This chapter will cover all the basic I/O functions available in Ruby. For more functions, please refer to Ruby Class IO.

Ruby Exceptions

The execution and the exception always go together. If you are opening a file, which does not exist, then if you did not handle this situation properly, then your program is considered to be of bad quality.
The program stops if an exception occurs. So exceptions are used to handle various type of errors, which may occur during a program execution and take appropriate action instead of halting program completely.