add a protected static property to a class in ruby

In Ruby, we can define a static property (i.e. class-level variable) with the @@ notation. To make it protected, we can use the protected_class_method or protected_singleton_method method.

Here's an example of how to define a protected static property in a class:

main.rb
class MyClass
  @@my_protected_static_property = 42

  protected_class_method :my_protected_static_property=

  def self.set_my_protected_static_property(value)
    @@my_protected_static_property = value
  end

  def self.get_my_protected_static_property
    @@my_protected_static_property
  end

  protected

  def self.my_protected_static_property=(value)
    @@my_protected_static_property = value
  end
end
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In this example, we define a static variable @@my_protected_static_property and a setter method my_protected_static_property= as protected. We also define a getter method get_my_protected_static_property and a public setter method set_my_protected_static_property that can be called from outside the class.

To access the protected static property, we can use the send method with the name of the protected method:

main.rb
MyClass.send(:my_protected_static_property=, 123)
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This code will set the value of the protected static property to 123. Note that we have to use send to call the protected method from outside the class.