Ruby：在另一个类的类方法中访问一个类的类实例变量

发布于 2024-10-17 23:54:18 字数 550 浏览 7 评论 0原文

我正在开发一个 ruby 程序并遇到了以下问题。

我有两个类 AClass 和 BClass 如下：

class AClass
  attr_accessor :avar
  def initialize(input)
    @avar = input
  end
end

class BClass
  def BClass.build(aclass)
    bvalue = aclass.avar
    ....
  end
end

当我运行时：

aclass = AClass.new           
puts aclass.avar              
bclass = BClass.build(aclass)

前两行工作正常。 aclass 被初始化并且 avar 被输出到屏幕上，但是第三行产生了错误。我似乎 BClass 构建方法无法访问 AClass 实例变量。我需要做什么才能使这项工作成功。我认为 attr_accessor 将使我能够访问 AClass 实例变量。预先感谢您的意见。

原文

I am working on a ruby program and have run into the following problem.

I have two classes AClass and BClass as follows:

class AClass
  attr_accessor :avar
  def initialize(input)
    @avar = input
  end
end

class BClass
  def BClass.build(aclass)
    bvalue = aclass.avar
    ....
  end
end

When i run:

aclass = AClass.new           
puts aclass.avar              
bclass = BClass.build(aclass)

The first two lines work fine. aclass is intialized and avar is put out to the screen, but the third line creates an error. I seems that the BClass build method can not access the AClass instance variable. What do I need to do to make this work. I thought the attr_accessor would enable me to access the AClass instance variables. Thanks in advance for your input.

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筱武穆 2024-10-24 23:54:18

如果要为 BClass 创建新类型的初始值设定项，可以执行以下操作：

class AClass
  attr_accessor :avar

  def initialize(input)
    @avar = input
  end
end

class BClass
  attr_accessor :bvalue

  def self.build(aclass)
    bclass = self.new
    bclass.bvalue = aclass.avar
    bclass
  end
end

aclass = AClass.new 'ruby'
bclass = BClass.build aclass

这将设置 bclass.bvalue = aclass.avar = 'ruby'。

If you want to create a new type of initializer for BClass, you can do the following:

class AClass
  attr_accessor :avar

  def initialize(input)
    @avar = input
  end
end

class BClass
  attr_accessor :bvalue

  def self.build(aclass)
    bclass = self.new
    bclass.bvalue = aclass.avar
    bclass
  end
end

aclass = AClass.new 'ruby'
bclass = BClass.build aclass

This will set bclass.bvalue = aclass.avar = 'ruby'.

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一直在等你来 2024-10-24 23:54:18

Mutu，你需要学习 ruby 的基础知识......你所拥有的甚至没有有效的 ruby 代码。

尝试运行这个。

class AClass
  attr_accessor :avar

  def initialize(input)
    @avar = input
  end
end

class BClass
  attr_reader :bvalue

  def initialize(aclass)
    @bvalue = aclass.avar
  end
end

在IRB中

ruby-1.9.2-p136 :077 > a = AClass.new('ruby')
 => #<AClass:0x00000100997298 @avar="ruby"> 
ruby-1.9.2-p136 :078 > b = BClass.new(a)
 => #<BClass:0x000001009921d0 @bvalue="ruby"> 
ruby-1.9.2-p136 :079 > b.bvalue
 => "ruby" 
ruby-1.9.2-p136 :080 > a.avar
 => "ruby"

Mutu, you need to learn the basics of ruby... what you have there is not even valid ruby code.

try running this.

class AClass
  attr_accessor :avar

  def initialize(input)
    @avar = input
  end
end

class BClass
  attr_reader :bvalue

  def initialize(aclass)
    @bvalue = aclass.avar
  end
end

in irb

ruby-1.9.2-p136 :077 > a = AClass.new('ruby')
 => #<AClass:0x00000100997298 @avar="ruby"> 
ruby-1.9.2-p136 :078 > b = BClass.new(a)
 => #<BClass:0x000001009921d0 @bvalue="ruby"> 
ruby-1.9.2-p136 :079 > b.bvalue
 => "ruby" 
ruby-1.9.2-p136 :080 > a.avar
 => "ruby"

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