Start Coding

Subjects

JAVASCRIPTHTMLCSSPYTHONSQLJAVACPPCSHARPPHPTYPESCRIPTCRUBYGOSWIFTKOTLINRUSTRBASHSCALAOBJECTIVE-CDARTPERLLUAMATLABXMLJSONMARKDOWNASSEMBLYLATEXYAMLSOLIDITYBLOCKCHAIN

Topics

Ruby Basics

Introduction to RubyInstalling RubyRuby SyntaxRuby CommentsRuby VariablesRuby Data TypesRuby OperatorsRuby ConstantsRuby OutputRuby InputRuby String Interpolation

Control Structures

Ruby If-Else StatementsRuby Case StatementsRuby Unless StatementRuby While LoopsRuby For LoopsRuby Each IteratorRuby Break and NextRuby Redo and Retry

Ruby Methods

Defining Ruby MethodsRuby Method ArgumentsRuby Default ArgumentsRuby Keyword ArgumentsRuby Variable ArgumentsRuby Return ValuesRuby Method Aliases

Ruby Collections

Ruby ArraysRuby Array MethodsRuby HashesRuby Hash MethodsRuby RangesRuby Sets

Ruby OOP

Ruby ClassesRuby ObjectsRuby InheritanceRuby ModulesRuby MixinsRuby EncapsulationRuby PolymorphismRuby Method OverridingRuby Class VariablesRuby Instance VariablesRuby Getters and SettersRuby attr_* Methods

Ruby Advanced Concepts

Ruby BlocksRuby ProcsRuby LambdasRuby ClosuresRuby MetaprogrammingRuby ReflectionRuby Dynamic Method CreationRuby Singleton ClassesRuby Method MissingRuby Symbols

Ruby Exception Handling

Ruby Begin-Rescue-EndRuby Raise ExceptionsRuby Custom ExceptionsRuby Ensure ClauseRuby Retry Statement

Ruby File I/O

Ruby File Open and CloseRuby File Read OperationsRuby File Write OperationsRuby File ModesRuby Directory Operations

Ruby Modules and Gems

Ruby Module CreationRuby Module InclusionRuby NamespacesRuby Gem BasicsRuby Gem InstallationRuby Bundler

Ruby Testing

Ruby Unit TestingRuby Test::Unit FrameworkRuby RSpec BasicsRuby Mocking and Stubbing

Ruby Concurrency

Ruby ThreadsRuby FibersRuby GIL (Global Interpreter Lock)Ruby Parallel Processing

Ruby and the Web

Ruby CGI ProgrammingRuby ERB TemplatesRuby and HTTPRuby JSON ParsingRuby XML Parsing

Ruby Performance

Ruby ProfilingRuby BenchmarkingRuby Memory ManagementRuby Garbage Collection

Ruby Best Practices

Ruby Code Style GuideRuby Naming ConventionsRuby Design PatternsRuby Refactoring Techniques

Ruby Class Variables

Class variables are an essential feature in Ruby's object-oriented programming paradigm. They allow data to be shared across all instances of a class, providing a way to maintain state at the class level.

What are Class Variables?

In Ruby, class variables are prefixed with @@ and are accessible to all instances of a class. They differ from instance variables, which are unique to each object.

Syntax and Usage

To define a class variable, use the following syntax:


class MyClass
  @@class_variable = initial_value
end

Class variables can be accessed and modified within instance methods, class methods, and the class definition itself.

Examples

Example 1: Counting Instances


class Person
  @@person_count = 0

  def initialize(name)
    @name = name
    @@person_count += 1
  end

  def self.total_count
    @@person_count
  end
end

person1 = Person.new("Alice")
person2 = Person.new("Bob")

puts Person.total_count  # Output: 2

In this example, @@person_count keeps track of the total number of Person instances created.

Example 2: Shared Configuration


class DatabaseConnection
  @@config = { host: 'localhost', port: 5432 }

  def self.config
    @@config
  end

  def self.update_config(new_config)
    @@config.merge!(new_config)
  end
end

puts DatabaseConnection.config
# Output: {:host=>"localhost", :port=>5432}

DatabaseConnection.update_config({ port: 3306 })
puts DatabaseConnection.config
# Output: {:host=>"localhost", :port=>3306}

Here, @@config stores shared configuration settings for database connections.

Best Practices and Considerations

  • Use class variables sparingly, as they can make code harder to maintain and test.
  • Be cautious when using class variables in inheritance hierarchies, as they are shared among subclasses.
  • Consider using class instance variables as an alternative for better encapsulation.
  • Avoid modifying class variables from instance methods to prevent unexpected behavior.

Context in Ruby OOP

Class variables play a crucial role in Ruby's object-oriented design. They complement instance variables and constants, offering a way to maintain state at the class level. This feature is particularly useful when implementing design patterns or managing shared resources across multiple instances.

Conclusion

Ruby class variables provide a powerful mechanism for sharing data across all instances of a class. While they offer unique capabilities, it's important to use them judiciously and be aware of their behavior in complex class hierarchies. Mastering class variables will enhance your ability to design efficient and maintainable Ruby programs.