Instance methods in Ruby

Introduction

Instance methods let objects do things or show information about themselves. They help organize code by grouping actions with the data they belong to.

When you want each object to have its own behavior, like a dog barking or a car driving.

When you need to get or change information stored inside an object.

When you want to keep related code together inside a class for easy understanding.

When you want to reuse code by calling methods on different objects of the same type.

Syntax

Ruby

class ClassName
  def method_name
    # code here
  end
end

Instance methods are defined inside a class using def.

You call instance methods on an object created from the class.

Examples

This defines a bark method for Dog objects.

Ruby

class Dog
  def bark
    puts "Woof!"
  end
end

This creates a Dog object and calls its bark method, printing "Woof!".

Ruby

dog = Dog.new
dog.bark

This method takes a name and says hello to that person.

Ruby

class Person
  def greet(name)
    puts "Hello, #{name}!"
  end
end

Calls the greet method with "Alice", printing a greeting.

Ruby

person = Person.new
person.greet("Alice")

Sample Program

This program creates a Car object with make and model. The description method returns a string describing the car. We print that description.

Ruby

class Car
  def initialize(make, model)
    @make = make
    @model = model
  end

  def description
    "This car is a #{@make} #{@model}."
  end
end

my_car = Car.new("Toyota", "Corolla")
puts my_car.description

Important Notes

Instance methods can access instance variables like @make inside the object.

You must create an object (instance) of the class to use instance methods.

Use initialize method to set up initial values when creating an object.

Summary

Instance methods belong to objects and define what they can do.

Define instance methods inside a class using def.

Call instance methods on objects created from the class.