如何在Ruby中初始化模块的实例变量？

Question

我有一些模块,我想在其中使用实例变量.我目前正在初始化它们:

module MyModule
  def self.method_a(param)
    @var ||= 0
    # other logic goes here
  end
end

我也可以调用init方法来初始化它们:

def init
  @var = 0
end

但这意味着我必须记住要经常打电话给它.

有没有更好的方法呢？

Answer 1

在模块定义中初始化它们.

module MyModule
  # self here is MyModule
  @species = "frog"
  @color = "red polka-dotted"
  @log = []

  def self.log(msg)
    # self here is still MyModule, so the instance variables are still available
    @log << msg
  end
  def self.show_log
    puts @log.map { |m| "A #@color #@species says #{m.inspect}" }
  end
end

MyModule.log "I like cheese."
MyModule.log "There's no mop!"
MyModule.show_log #=> A red polka-dotted frog says "I like cheese."
                  #   A red polka-dotted frog says "There's no mop!"

这将在定义模块时设置实例变量.请记住,您可以稍后重新打开模块以添加更多实例变量和方法定义,或者重新定义现有模块:

# continued from above...
module MyModule
  @verb = "shouts"
  def self.show_log
    puts @log.map { |m| "A #@color #@species #@verb #{m.inspect}" }
  end
end
MyModule.log "What's going on?"
MyModule.show_log #=> A red polka-dotted frog shouts "I like cheese."
                  #   A red polka-dotted frog shouts "There's no mop!"
                  #   A red polka-dotted frog shouts "What's going on?"

Answer 2

您可以使用:

def init(var=0)
 @var = var
end

如果你没有传递任何东西,它将默认为0.

如果你不想每次都打电话,你可以使用这样的东西:

module AppConfiguration
   mattr_accessor :google_api_key
   self.google_api_key = "123456789"
...

end