In Ruby, class variables are attached to the class in which they are declared. A class variable should be declared with two
@ symbols preceding it.
class Child@@children = 0def initialize(name, birth_year)@name = name@birth_year = birth_year@@children +=1enddef self.children_addedreturn @@childrenendendnaomi = Child.new("Naomi", 2006)bertha = Child.new("Bertha", 2008)puts Child.children_added # => 2
In Ruby, a new class instance can be created by calling the
.new method of the class. Arguments to the class’
initialize method can be passed in to the
class Fighterdef initialize(name, style, division, age)@name = name@style = style@division = division@age = ageendendconor = Fighter.new("Conor", "mixed martial arts", "Welterweight", 31)
In Ruby, the
@ symbol is used to signify an instance variable. Instance variables hold a value specific to each instance of that class, not to all members of the class itself.
class Studentdef initialize(name, grade)@name = name@grade = gradeendend# In this example, name and grade are the instance variables.
In a Ruby class, an
initialize method is used to generate new instances of the class. It is usually the first method of a class.
class Persondef initialize# this code runs when a new instance is createdendend#Every time Person.new is called, the initialize method of the Person class is called.
A Ruby class is used to organize and model objects with similar attributes and methods.
class NewClass# code for this classend# A basic class definition consists of the class keyword, the name of the class in CamelCase (with the first letter capitalized) format, and an end keyword.
super keyword is used to directly access the attributes or methods of a superclass. This means a class with
super will inherit the attributes or methods of a superclass.
class Tripdef initialize(duration, price)@duration = duration@price = priceendendclass Cruise < Tripdef initialize(duration, price)superendendspain_backpacking = Trip.new(14, 800.00)carnival = Cruise.new(7, 2400.00)#In this example, the Cruise class inherits from the Trip class and all of its attributes, including duration and price, are carried over with the super keyword.
attr_writer are methods used to read and write variables, respectively.
class Studentattr_reader :nameattr_writer :namedef initialize(name)@name = nameendend#In this example, Ruby is able to both read and write the @name instance variable since it was passed to attr_reader and attr_writer as a symbol.top_student = Student.new("Jyothi")puts top_student.name # => Jyothi#In classes with attr_reader, instance variables can be accessed using . notationputs top_student.name # => Jyothitop_student.name = "Anika"puts top_student.name # => Anika#In classes with attr_writer, instance variables can be reassigned using . notation