Ruby Constants, What Are They?

When discussing programming languages known for their flexibility and ease of use, Ruby consistently ranks high. Since its launch, Ruby has gained widespread popularity, thanks to its user-friendly features like Ruby constants. The future of Ruby already looks bright, and its versatility continues to attract developers globally.

Created in 1995 by Yukihiro Matsumoto, Ruby was designed to combine code reuse and object-oriented programming, offering developers a faster and more efficient way to build applications. This high-level language is known for its intuitive, English-like syntax, allowing developers to code with minimal interaction with machine language. As a scripting language, Ruby is written as text and later interpreted into code.

Ruby’s flexibility, coupled with its open-source nature that lets developers modify parts of the language, has made it a beloved choice for various applications. While web development remains its most common use, Ruby is also used for web servers, data processing, DevOps, static site generation, and more.

In this article, we’ll explore one of Ruby’s standout features — Ruby constants — and how they contribute to the language's functionality in development.

What are Ruby Constants?

Regardless of the programming language, coding requires you to assign values to specific elements to be used across the code. This is where variables come in. Variables are present in every programming language and are essential to the Ruby coding system. Ruby constants are a special type of variable. As the name implies, it's a variable whose value is expected to remain the same throughout the program.

Before going further into constants, it’s crucial to understand Ruby variables.

What are Ruby Variables?

In programming, a variable is a name representing a program's value. Variables are used to store different values — including character strings, numeric values, and memory addresses — for use in any part of the program when they're required. It isn’t any different in the Ruby programming language. Ruby supports 5 types of variables in every program:

• Local Variables: Represented by starting with a lowercase letter (e.g., number) or an underscore (_number).
• Instance Variables: Defined by starting with the “@” character, these variables are shared in all the methods for the particular object in the variable.
• Class Variable: Represented by starting with “@@,” class variables share the values between a class, its subclasses, and its instances.
• Global Variables: Defined by starting with a “$” sign, global variables are accessible anywhere within the Ruby program.
• Ruby Constants: A special type of variable beginning with an uppercase letter as its representation (e.g., Name).

What Makes Ruby Constants Special?

Although constants are a type of variable in Ruby, certain features distinguish them. The prominent feature that makes constants unique is that you can easily change a variable's value at any time in the program. In contrast, the value assigned to constants remains the same throughout the program. This is the same across every programming language.

However, Ruby constants have a slight variation. In Ruby, you can change the value assigned to any constant in the code, but by doing this, Ruby will give a warning. Unlike other programming languages that will not run the code or give error messages before effecting changes, Ruby lets you change constant values with a slap on the hand. But it notifies you of the activity with a line like "Warning: already initialized constant," although it'll reflect the value of the constant you wrote. That makes it special, as it is one of the pros of Ruby's development.

These constants can be defined by starting with an uppercase letter as the first letter or making the whole constant all caps. That is, writing Rate = (any value you assign) or RATE = (any value you assign). This distinguishes it from other program listings.

Ruby Constants and Methods

Another special feature of Ruby constants is that they can’t be defined inside a method. In Ruby, a method works similarly to a function in other programming languages. These methods are used to group one or more repeatable statements into one unit.

A method works as a set of expressions that returns a value. Methods let you have subroutines that can be called from other program areas. So, if you define a constant inside a method like this, it'll fail with a syntax error.

However, there are certain ways to bypass this. Metaprogramming tricks can give you a chance to use your constant inside a select number of methods, including const_get (returns the value for a constant), remove_cont (removes a constant), and many more.

Ruby Literals

It's impossible to go on without mentioning literal when talking about Ruby constants. Literals are used every time an object is typed into the Ruby code. Literals are any constant value that can be assigned to a variable or constant in the code. They're special syntaxes that create a specific type of object used in the program.

There are different types of Ruby Literals, and some of them include:

• Booleans and nil (Boolean constants true, false, nil)
• Numbers or integers
• Symbol
• Range (prints all the possible values in the given boundaries)
• Array (a collection of objects created with special brackets [ and ] )
• Hashes (used as perfect keys)

Ruby Constants and Global Variables

Constants and global variables are two different types of variables across different programming languages. Despite their different classifications and uses, they have quite a number of similarities. Their differences, however, depend on what programming language they use. In the Ruby programming language, constants and global variables have a range of similarities and differences.

In Ruby, constants and global variables are very similar. They both run outside of a method, assigning values to literals on the code. Constants also have the visibility of a global variable. This means you can use a constant anywhere in a Ruby program without paying too much attention to the scope. However, a significant difference between them is the ability to change values. You can change the value of a global variable in Ruby easily. However, as it has already been established for a Ruby constant, its value will only change, accompanied by a warning from Ruby.

So, a Ruby constant is like a global variable with a warning for value changes. Also, assigning a value to a global variable changes the global status of that variable. Another difference between a constant and a global variable in Ruby is that constants can be defined by modules and classes — unlike global variables — so they can have qualified names.

Ruby constants are a unique kind of constant in the programming world. The ability of the constant to be somewhat dynamic is what makes it special. Regardless of how you might be using the Ruby constant in your programs, it's going to be a different experience whether you’re using Ruby or Ruby on Rails.

FAQs

Q1. How do you use a constant in Ruby?

You have to first declare a constant to use it. There are 2 ways to do this. Your first option is to begin the first letter of the constant with an uppercase letter, and there you have it. On the other hand, you can decide to type the whole constant in uppercase. These are the simple ways to use a constant in Ruby.

The simplicity of the entire programming and scripting language known as Ruby is one of the reasons it's everybody's favorite. The simplicity also extends to the Ruby Constant.

Q2. Are constants global in Ruby?

In the Ruby programming language, constants and global variables are two different kinds of variables. A constant and a global variable have a number of differences, the major one being the ability to easily change the value of a global variable without getting a warning.

Despite the differences, constants and global variables have shared commonalities. One of them is the visibility of a global variable in Ruby. Yes, constants are global on Ruby. You can use a constant anywhere on Ruby without bothering too much scope.

Q3. What are variables in Ruby?

Variables are used to store a value on Ruby and are instrumental in helping you recall these values when needed during the program. There are 5 types of variables in Ruby. They include local variables, instance variables, class variables, global variables, and constants. Like every other programming language, Ruby enables the use of variables to be able to use values all through the code. These variables are used as a means of storage for names, strings, characters, and many more as values in a code.