Ruby 如何处理嵌套类的继承？

Question

在以下测试用例中：

class Package
    class Component
        def initialize
            p [:initialize,self]
        end
    end
end

class Package_A < Package
end

class Package_B < Package
end

# Why are the following components of type Package and not Package_A and Package_B
component=Package_A::Component.new
p component

component=Package_B::Component.new
p component

结果：

[:initialize, #<Package::Component_1:0x2c0a8f8>]
#<Package::Component:0x2c0a8f8>
[:initialize, #<Package::Component_1:0x2c0a5b0>]
#<Package::Component:0x2c0a

如何获取特定的 Package_A.component 和 Package_B.component？

Answer 1

Component 类在 Package 中声明，所以看起来是正确的。 :: 告诉在Package_A 的范围内查找名称Component。由于那里没有Component，它会查找超类。

这个例子展示了如何实现你想要的。可能有更简单的方法，我很高兴看到它。

class Package
  class Component
    def foo
      puts "bar"
    end
  end
end

class Pack_a < Package
end

Pack_a::Component.new.foo
#=> bar
# as expected, though we actually have Package::Component

class Pack_b < Package
  class Component
  end
end

Pack_b::Component.new.foo
#=> NoMethodError: undefined method 'foo' for Pack_b::Component
# this error is because Pack_b::Component has nothing to do with Package::Component

class Pack_c < Package
  class Component < Package::Component
  end
end

Pack_c::Component.new.foo
#=> bar
# as expected

Pack_c::Component.new
#=> Pack_c::Component
# this Component is a subclass of Package::Component

这个 more-less 应该解释作用域在这种情况下是如何工作的。希望这会有所帮助。