Question

我想跟踪一个类的所有实例，以下代码完美无缺，但不是很干。

class BaseClass
end

class ClassA < BaseClass
  @@instances = []
  attr_accessor :name

  def initialize(name)
    @name = name
    @@instances << self
  end
  def self.list
    @@instances
  end
  def to_s
    @name
  end
end

class ClassB < BaseClass
  @@instances = []
  attr_accessor :name

  def initialize(name)
    @name = name
    @@instances << self
  end
  def self.list
    @@instances
  end
  def to_s
    @name
  end
end

puts "Creating instances"
a = ClassA.new "a"
aa = ClassA.new "aa"
b = ClassB.new "b"

puts "Listing for ClassA"
puts ClassA.list
puts "Listing for ClassB"
puts ClassB.list

其输出变为

Creating instances
Listing for ClassA
a
aa
Listing for ClassB
b

完美。但是，当我尝试重复删除它时

class BaseClass
  @@instances = []
  attr_accessor :name

  def initialize(name)
    @name = name
    @@instances << self
  end
  def self.list
    @@instances
  end
  def to_s
    @name
  end
end

class ClassA < BaseClass
end

class ClassB < BaseClass
end

puts "Creating instances"
a = ClassA.new "a"
aa = ClassA.new "aa"
b = ClassB.new "b"

puts "Listing for ClassA"
puts ClassA.list
puts "Listing for ClassB"
puts ClassB.list

我得到以下输出

Creating instances
Listing for ClassA
a
aa
b
Listing for ClassB
a
aa
b

这是有道理的，因为@@instances中定义了BaseClass，并与ClassA和ClassB共享。

如何让我的代码重复数据删除看起来像后一个例子，这样它的行为就像前一个例子一样？

Answer 1

最简单的方法是摆脱你想要做的伎俩，然后使用ObjectSpace.each_object。

class BaseClass
  attr_accessor :name
  def initialize(name); @name = name end
  def to_s; @name end
end

class ClassA < BaseClass; end

class ClassB < BaseClass; end

puts "Creating instances"
a = ClassA.new "a"
aa = ClassA.new "aa"
b = ClassB.new "b"
puts "Listing for ClassA"
puts ObjectSpace.each_object(ClassA).to_a
puts "Listing for ClassB"
puts ObjectSpace.each_object(ClassB).to_a

这给出了

Creating instances
Listing for ClassA
aa
a
Listing for ClassB
b

Ruby重复数据删除和跟踪实例

1 个答案: