Ruby on rails 在Ruby中，我可以在initialize方法中自动填充实例变量吗？

在Ruby中，我可以在initialize方法中自动填充实例变量吗

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

为了保持简单：

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

您可以通过元编程来做一些更聪明的事情，但这真的有必要吗？

您可以这样使用：

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

我建议

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

---

Ruby有时很简单。看不见有环

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

测试：

注意，这实际上并没有设置实例变量。您的类将有不透明的getter和setter。如果您不想公开它们，可以围绕它包装另一个类。下面是一个例子：

# 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

---

我想你可以简单地说：

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

---

我理解避免不必要的元编程的愿望，但这并不是OP所要求的简洁代码。你必须手动指定每个字段名。我回来回答两年前看到的这个问题，只是为了找到一年前给出我心中答案的人。（但我更喜欢

class Weekend

一个常量

可用的\u属性如何，而不是一个类变量？@BKSpurgeon我不知道它有多常见。如果你打算在团队项目中使用它，我建议询问团队是否接受它。
# 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

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

class Weekend
#whatever you need to add here
end