Question

我有几个继承自单个类的类。每个子类创建一些数据结构，然后父类对该数据执行操作。

问题：无论对象是否已实例化，如何让父类使用该数据。

class A
  def self.static_test
    puts @myvar + "_static"
  end
  def instantiated_test
    puts @myvar + "_instantiated"
  end
end
class B<A
  @myvar = "this works B"
end
class C<A
  @myvar = "this works C"
end

B.static_test
B.new.instantiated_test
C.static_test
C.new.instantiated_test
B.static_test
B.new.instantiated_test

我需要上面的代码来打印：

this works B_static
this works B_instantiated
this works C_static
this works C_instantiated
this works B_static
this works B_instantiated

我使用的是Ruby 1.8.7。

编辑：看起来我的原始问题有点令人困惑。我需要静态和实例化方法来使用相同的数据。但是这些方法不会做同样的事情。我更新了示例代码以反映这一点。

Answer 1

def instantiated_test
  self.class.static_test
end

顺便说一句，如果您确定继承的类具有某种结构，请将其提取到父类。如果您不确定，请不要在父类中使用它。家长的实施不应该取决于孩子的实施。

Answer 2

class A
  class << self
    attr_reader :myvar
  end
  # Alternatively:
  # def self.myvar; @myvar; end

  def self.static_test
    puts myvar
  end
  def instantiated_test
    puts self.class.myvar
  end
end
class B<A
  @myvar = "this works B"
end
class C<A
  @myvar = "this works C"
end

B.static_test
#=> this works B
B.new.instantiated_test
#=> this works B
C.static_test
#=>this works C
C.new.instantiated_test
#=>this works C
B.static_test
#=> this works B
B.new.instantiated_test
#=> this works B

Answer 3

class A
  def self.static_test
    puts @myvar
  end
  def instantiated_test
    puts @myvar
  end
end
class B<A
  @myvar = "this works B"
  @@myvar = @myvar
  def initialize
    @myvar = @@myvar
  end
end
class C<A
  @myvar = "this works C"
  @@myvar = @myvar
  def initialize
    @myvar = @@myvar
  end
end

但这很难看，需要重复。

用继承传递数据？

3 个答案: