ruby 如何从超类初始化关键字参数（对依赖注入很有用）

Posted 2021-05-15

# http://ruby-doc.org/core-2.4.0/doc/syntax/calling_methods_rdoc.html#label-Hash+to+Keyword+Arguments+Conversion
class Super
  attr_reader :shared

  # ServiceObject style class-level activation method
  def self.run(**args)
    new(**args).tap{ |obj| obj.run }
  end

  def initialize(shared: 'All subclasses see me', **args)
    @shared = shared
  end
end

class Child < Super
  def initialize(special: nil, **args)
    super # this reads **args implicitly!
    @special = special
  end

  def run
    puts "Shared:#{shared} Special:#{@special}"
  end
end

Child.run(special: 2)
# Shared:All subclasses see me Special:2 

Child.run(shared: "super", special: 2)
# Shared:super Special:2