ruby - Gem 中的配置 block

Question

我正在尝试编写我的第一个 gem，但对典型配置 block 的工作方式有点困惑。为了说明，我想要的是编写类似

MyGem.configure do |c|
    c.property1 = 1
    c.property2 = 'some string'
end

我的 ruby​​ 知识不够深，所以虽然我很乐意使用 block ，但我不确定如何编写需要 block 的代码。

如何以这种方式编写要配置的“MyGem”类(大概通过实例变量)？

Answer 1

这可能是实现您的示例的方式:

class MyGem
  Config = Struct.new :property1, :property2  # => MyGem::Config

  def self.configure(&config_block)
    config_block.call config         # => "some string"
  end                                # => :configure

  def self.config
    @config ||= Config.new  # => #<struct MyGem::Config property1=nil, property2=nil>, #<struct MyGem::Config property1=1, property2="some string">
  end                       # => :config
end                         # => :config

MyGem.configure do |c|         # => MyGem
  c.property1 = 1              # => 1
  c.property2 = 'some string'  # => "some string"
end                            # => "some string"

MyGem.config  # => #<struct MyGem::Config property1=1, property2="some string">

但我也提倡在实例而不是类上存储状态:

class MyGem
  Config = Struct.new :property1, :property2  # => MyGem::Config
  def initialize(&config_block)
    config_block.call config                  # => "some string"
  end                                         # => :initialize

  def config
    @config ||= Config.new  # => #<struct MyGem::Config property1=nil, property2=nil>, #<struct MyGem::Config property1=1, property2="some string">
  end                       # => :config
end                         # => :config

instance = MyGem.new do |c|    # => MyGem
  c.property1 = 1              # => 1
  c.property2 = 'some string'  # => "some string"
end                            # => #<MyGem:0x007fc1691ecb20 @config=#<struct MyGem::Config property1=1, property2="some string">>

instance.config  # => #<struct MyGem::Config property1=1, property2="some string">

如果你这样做，你就没有全局状态。请注意，我们可以有多个不同的配置(例如，每个客户端都有自己的配置，或者您想编写多个测试，但现在每个都有破坏其他配置的风险)。我写了一篇博客，介绍了我想到的实现单例模式的许多方法，以及为什么不应该这样做:http://blog.8thlight.com/josh-cheek/2012/10/20/implementing-and-testing-the-singleton-pattern-in-ruby.html