Constant References in ruby

Constant Can Change

Constant References in ruby can change, as we have seen in the introduction.

Example:

AXE = 1
AXE = 2
puts AXE

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Output:

main.rb:2: warning: already initialized constant AXE
main.rb:1: warning: previous definition of AXE was here
2

From the example above, we saw that Ruby doesn’t stop us from changing the value of the constant. But, it throws a warning. Our program will continue to function normally, but we must avoid this.

We can create an immutable constant by using the freeze keyword.

Example:

PLAYER = "saurabh yadav".freeze
PLAYER << "o"
puts PLAYER

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Output:

main.rb:2:in `<main>': can't modify frozen String (RuntimeError)

Constant Methods

There are a few approaches to dealing with constants:

These methods can be used to perform a few metaprogramming tricks.

Example:

module Snacks
  class Chips; end
  class MilkChocolate; end
end

puts "Classes defined inside #{Snacks}:"
puts Snacks.constants

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Output:

Classes defined inside Snacks:
Chips
MilkChocolate

Ruby Constant Scope

When we create a constant outside of any class, at the top of your code, it is available everywhere.

Constants specified outside of a nested module or class are available within the nested classes as well.

module Snacks
STORE_ADDRESS = "Milk"
class Chocolate
def foo; puts STORE_ADDRESS; end
end
end
fb = Snacks::Chocolate.new
fb.foo

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Output:

Milk

Constants are also available in child classes.

class Snacks
def Lassi
"Lassi is not good"
end
end
class Chocolate < Snacks
def Lassi
"Lassi is good"
end
end
p Snacks.new.Lassi 
p Chocolate.new.Lassi

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Output:

"Lassi is not good"
"Lassi is good"

Frequently Asked Questions

What are Ruby variables?

Variables in Ruby store data that may be utilized later in a program. Each variable serves as a memory and is given a unique name.\

There are four types of variables in Ruby:

• Local variable
• Class variable
• Instance variable
• Global variable

What is a global constant in Ruby?

The environment variable for the entire program is an example of a global constant. Let's look at some examples of Ruby constant lists: We'll look at constants defined at the top of the program and how to use them both inside and outside of it in this example.

What is the definition of a class constant in Ruby?

Class constants can be useful if you need to define some constant data within a class.

Constants of the class, the name of a constant begins with an uppercase letter. It should only be given a value once. Reassignment of a constant generates a warning but not an error in the current Ruby implementation (the non-ANSI version of eval .rb does not report the warning).

Is String Literal in Ruby Mutable?

The []= method in Ruby can be used to modify a portion of a string. To use this function, simply supply the string of characters to be replaced and assign the new string to the method.

Why are Ruby classes constant, and why is it important?

You're getting an " uninitialized constant " error because you most likely forgot to require a file or gem that defines the constant, you're getting an "uninitialized constant" error.

Conclusion

In this article, we have extensively discussed the concept of the Constant References in ruby. We started with the introduction of Constant References in ruby, uninitialized constant error, Constant method references in ruby, and scope of Constant References in ruby.

After reading about the Constant References in ruby, are you not feeling excited to read/explore more articles on the topic of ruby? Don't worry; Coding Ninjas has you covered. To learn, see  String literal in Ruby, Constants in Ruby, and Methods in Ruby.

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