Class Methods And Variables In Ruby On Rails

INTRODUCTION

Today, we are going to see the class methods, variables, and the to_s method in Ruby programming language. The brief description of this concept is given below.

Class Variables.
Class Constants.
The to_s method.

CLASS VARIABLES

Class variables are accessible to every object of a class.
A class variable belongs to the class, not the object.
You declare a class variable using two @signs for example, @@name.
We can, for example, keep count of all person objects created using a class variable.

EXAMPLE

Class person
@@count = 0
def initialize
@@count + =1
End
def self.get_count
@@count
End
End
P1 =person.new If we use only p1
P2 =person.new means the output is 1.
Puts person.get_count

Output

In the code above, @@count is a class variable.
Since the initialize method is called for every object that is created, incrementing the @@count variable will keep track of the number of objects created.
We also defined a class method called get_count to return the value of the class variable.
In the code above, we have created two objects of the person so the value of the @@count variable is 2.
A class variable is usually used when you need information about the class, not the individual objects.

CLASS CONSTANTS

A class can also contain constants.
Remember, constant variables do not change their value and start with a capital letter.
It is common to have uppercase names for constants.

Example

Class calc
PI = 3.14
End

You can access constants using the class name, followed by two colon symbols (::) and the constant name. For example -

Example

Puts calc :: PI

Output

3.14

THE TO_S METHOD

The to_s method comes built-in with all classes.
It gets called when you output the object.

Example

Class person
# some code
End
P = person.new
Puts P

Output

#<person:0x0000000271e128>

When we call puts p, Ruby automatically calls the to_s method for the object p, so puts p is the same as puts p.to_s.
By default, the to_s method prints the object’s class and an encoding of the object id.
We can define our own to_s method for a class and add custom implementation to it.
For example, we can generate an informative, formatted output for our person class.

Example

Class person
def initialize(n,a)
@name = n
@age = a
End
def to_s
#{@name} is # {@age} years old.
End
End
P = person.new(“David”, 28)
Puts P

Output

David is 28 years old.

The to_s method also gets called when the object is used as a value in a string, like”#{P}”.
Defining the to_s method makes it easier and shorter to output the information of an object in the format needed, as opposed to defining a custom method and calling it from an object.
When you define the to_s method, you call puts on your object (puts obj) where with a custom method, you have to explicitly call it from the object (puts obj.info).

CONCLUSION

In this write-up, we learned some new concepts in Ruby. I hope it will help you gain more knowledge. In the future, we will go deeper into the concepts of Ruby programming.

INTRODUCTION

CONTENTS

CLASS VARIABLES

CLASS CONSTANTS

THE TO_S METHOD

CONCLUSION