未初始化的常量A :: B（NameError）

Question

This works:

class A
    def m1
         b = B.new
    end
end

class B
end

This fails - why?

class A
   b = B.new
end

class B
end

Error message "'': uninitialized constant A::B (NameError)" is rased.

Answer 1

因为在第二个代码中， b = B.new是在定义B之前求值的。