带有默认值的参数哈希的 Ruby 方法：如何 DRY？

发布于 2024-11-05 16:03:46 字数 713 浏览 0 评论 0原文

我有一个 initialize 方法，它接受哈希值来设置一些实例变量。这基本上就是我想要做的：

class Ad
  DEFAULT_PAGE = 'index'.freeze

  DEFAULT_CHANNEL = 'general'.freeze

  DEFAULT_AREA = 'general'.freeze

  attr_accessor :page, :area, :channel

  def initialize args={}
    @page = args[:page] || DEFAULT_PAGE
    @area = args[:area] || DEFAULT_AREA
    @channel = args[:channel] || DEFAULT_CHANNEL
  end

  # ...
end

我看到了一个允许动态设置实例变量的提示，但我不确定如何也包含默认值...

  def initialize args={}
    args.each do |attr,val|
      instance_variable_set("@#{attr}", val) unless val.nil?
    end
  end

我可以动态引用常量吗？或者有任何更好的方法来做这类事情，欢迎！

...我还意识到 attr_accessor 变量可以单独设置。但我只想这样做。 :)

原文

I have an initialize method that accepts a hash to set some instance variables. This is basically what I'm trying to do:

class Ad
  DEFAULT_PAGE = 'index'.freeze

  DEFAULT_CHANNEL = 'general'.freeze

  DEFAULT_AREA = 'general'.freeze

  attr_accessor :page, :area, :channel

  def initialize args={}
    @page = args[:page] || DEFAULT_PAGE
    @area = args[:area] || DEFAULT_AREA
    @channel = args[:channel] || DEFAULT_CHANNEL
  end

  # ...
end

I saw a tip to allow dynamic setting of instance variables, but I'm not sure how to also include the default values...

  def initialize args={}
    args.each do |attr,val|
      instance_variable_set("@#{attr}", val) unless val.nil?
    end
  end

Can I refer to a constant dynamically? Or any better ways of doing this sort of thing are welcome!

... I also realize that attr_accessor variables can be set individually. But I just want to do it like this. :)

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樱花细雨 2024-11-12 16:03:46

如果实例变量位于您的 defaults 哈希中，则此变量也仅创建它们，这样您就不会意外创建/覆盖其他实例变量。

我假设您的意思是除非 val.nil？：

def initialize(args={})
  defaults = {
    :page    => DEFAULT_PAGE,
    :area    => DEFAULT_AREA,
    :channel => DEFAULT_CHANNEL
  }.merge(args).each do |attr, val|
    instance_variable_set("@#{attr}", val) if defaults.has_key?(attr) && (not val.nil?)
  end if args
end

This one also only creates the instance variables if they are in your defaults hash, so that you don't accidentally create/overwrite other instance variables.

I'm assuming you meant to say unless val.nil?:

def initialize(args={})
  defaults = {
    :page    => DEFAULT_PAGE,
    :area    => DEFAULT_AREA,
    :channel => DEFAULT_CHANNEL
  }.merge(args).each do |attr, val|
    instance_variable_set("@#{attr}", val) if defaults.has_key?(attr) && (not val.nil?)
  end if args
end

回复收藏 0 原文

娜些时光，永不杰束 2024-11-12 16:03:46

试试这个：

  def initialize args={}
    defaults = {
      :page    => DEFAULT_AREA, 
      :area    => DEFAULT_AREA, 
      :channel => DEFAULT_CHANNEL
    }
    args.reverse_merge(defaults).each do |attr,val|
      instance_variable_set("@#{attr}", val) unless val.nil?
    end
  end

Try this:

  def initialize args={}
    defaults = {
      :page    => DEFAULT_AREA, 
      :area    => DEFAULT_AREA, 
      :channel => DEFAULT_CHANNEL
    }
    args.reverse_merge(defaults).each do |attr,val|
      instance_variable_set("@#{attr}", val) unless val.nil?
    end
  end

回复收藏 0 原文

~没有更多了~