Ruby classes and instances


This will be a memo for learning.

In Ruby, many terms such as "object" and "variable" come out and it is difficult, so I would like to output it in my own way to speed up understanding even little by little. If there are any differences, I would appreciate it if you could comment.

What are classes and instances?

To understand classes and instances, we need to understand the terms "object" and "method".

The explanation is below ...


An object is " all data in Ruby ".

For example, characters such as "good morning" are called "character string objects", and numbers such as "123" are called "numeric objects".


The "processing" of an object is called a method. Every Ruby object has a "method". For example, like this

-Character string object-> length method-> count the number of characters -Numeric object-> to_s method-> Convert to integer

The methods that each object type has are different. For example, each person has a different personality.


A class is a " collection of common properties and methods ", and this time, we will consider a "car blueprint" as an example. When you make a car, you need a blueprint, but all cars have something in common (such as "accelerating" with the steering wheel and brakes). That is, "let's put together the common parts in a blueprint."

In other words, it is a mechanism that allows you to create a class (blueprint) so that you can use it when making other cars.


An instance is a " object created by inheriting attributes and processing from a class ".

Is it easy to understand an object (car) created based on a class (blueprint)? Since it inherits the minimum necessary parts, it is an advantage that you do not have to make a blueprint such as "There is a handle" from scratch.

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