Today I Learned

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Class.new with Superclass

Today I encountered the following syntax (observed in Ruby 2.7):

SpecialError = Class.new(StandardError)

What’s going on here?

According to the Class docs, Class.new takes a superclass as an argument, creating an anonymous unnamed class. So this could be written as:

class SpecialError < StandardError
end

We’d lose the anonymity of the SpecialError class, but in the first example, we are assigning it to a Pascal-cased variable name anyway.

I think the first syntax would make sense when the code looks just like this example: a simple class that inherits some behavior, where the name is needed only in the scope where the class is declared.

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