在Ruby中我可以在initialize方法中以某種方式自動填充實例變量嗎？

Question

在Ruby中我可以在initialize方法中以某種方式自動填充實例變量嗎？

例如，如果我有：

class Weekend
  attr_accessor :start_date, :end_date, :title, :description, :location

  def initialize(params)
    # SOMETHING HERE TO AUTO POPULATE INSTANCE VARIABLES WITH APPROPRIATE PARAMS
  end

end

Answer 1

您可以像這樣使用instance_variable_set ：

params.each do |key, value|
  self.instance_variable_set("@#{key}".to_sym, value)
end

Answer 2

為了簡單起見：

class Weekend
  attr_accessor :start_date, :end_date, :title, :description, :location

  def initialize(params)
    @start_date = params[:start_date] # I don't really know the structure of params but you have the idea
    @end_date   = params[:end_date]
  end
end

你可以通過元編程的方式做一些更聰明的事情，但這真的有必要嗎？

Answer 3

Ruby有時可能很簡單。 看不到循環！

class Weekend < Struct.new(:start_date, :end_date, :title, :description, :location)
  # params: Hash with symbols as keys
  def initialize(params)
    # arg splatting to the rescue
    super( * params.values_at( * self.class.members ) )
  end
end

請注意，您甚至不需要使用繼承 - 可以在創建期間自定義新的Struct ：

Weekend = Struct.new(:start_date, :end_date, :title, :description, :location) do
  def initialize(params)
    # same as above
  end
end

測試：

weekend = Weekend.new(
  :start_date => 'start_date value',
  :end_date => 'end_date value',
  :title => 'title value',
  :description => 'description value',
  :location => 'location value'
)

p [:start_date , weekend.start_date  ]
p [:end_date   , weekend.end_date    ]
p [:title      , weekend.title       ]
p [:description, weekend.description ]
p [:location   , weekend.location    ]

請注意，這實際上並不設置實例變量。 你的課將有不透明的getter和setter。 如果您不想暴露它們，可以在它周圍包裝另一個類。 這是一個例子：

# this gives you more control over readers/writers
require 'forwardable'
class Weekend
  MyStruct = ::Struct.new(:start_date, :end_date, :title, :description, :location)
  extend Forwardable
  # only set up readers
  def_delegators :@struct, *MyStruct.members

  # params: Hash with symbols as keys
  def initialize(params)
    # arg splatting to the rescue
    @struct = MyStruct.new( * params.values_at( * MyStruct.members ) )
  end
end

Answer 4

我想你可以簡單地說：

Weekend < Struct.new(:start_date, :end_date, :title, :description, :location)

然后在周末課程中添加其他內容：

class Weekend
#whatever you need to add here
end

Answer 5

我建議

class Weekend
  @@available_attributes = [:start_date, :end_date, :title, :description, :location]
  attr_accessor *@@available_attributes

  def initialize(params)
    params.each do |key,value|
      self.send(:"#{key}=",value) if @@available_attributes.include?(key.to_sym)
    end
  end
end