Automatic class level initialization in Ruby

Question

In Java, we can initialize the class level as follows: this piece of code will be called automatically when the class is initialized. Can we achieve a similar effect in Ruby?

static { initialization per class } 

Answer 1

Just add your code directly to the class body:

 class MyClass @my_var = 'init1' my_method 'init2' def self.my_method(param) end end 

This code will be called when the class is loaded.

PS: If you are working on a Rails project, you may already be familiar with this concept:

 class MyModel < ActiveRecord::Base has_many belongs_to validates scope end 

All of these methods are executed at the class level.

Answer 2

Ruby classes are open, which means you can modify them in different places and at runtime. Therefore, ruby ​​does not have class initialization.

However, any code inside your class definition will execute:

 class A def foo end print 'Declaring class A' end class A def bar end print 'Adding methods to class A' end