Why?

one more unnecessary noname class?

Agree, what is the profit?

When subclassing from Struct.new(...), you actually do that: Wheel = Class.new(Struct.new(...)), i.e. create two classes instead one and pollute ancestors chain with anonymous class:

class Wheel < Struct.new(:rim, :tire)
end
Wheel2 = Struct.new(:rim, :tire) do
end

p Wheel.ancestors # => [Wheel, #<Class:0x00000000ce7c28>, Struct, Enumerable, Object, Kernel, BasicObject]
p Wheel2.ancestors # => [Wheel2, Struct, Enumerable, Object, Kernel, BasicObject]

@ademidov thanks a lot for explanation, great example!

Another reason is because you cannot use Kernel#load to re-load a file that creates a subclass of Struct (type mismatch, since your subclass already has a parent).

Read the documentation for Struct.new

Struct.new("Wheel", :rim, :tire)

@postmodern Struct.new allows for both versions, shown by the example:

Struct.new("Wheel", :rim, :tire) # => Struct::Wheel
Wheel = Struct.new(:rim, :tire)  # => Wheel

Also, what if you need to add additional methods to your Struct, but don't want to write all that boilerplate initialization code? Should we be using something like Values or Virtus instead?