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)?
最佳答案
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
关于ruby - Gem 中的配置 block ,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/28177847/