Ruby中的跨领域日志记录
我正在尝试从外部向方法添加日志记录（面向方面的样式）
class A def test puts "I'm Doing something..." end end class A # with logging! alias_method :test_orig, :test def test puts "Log Message!" test_orig end end a = A.new a.test 上面的工作没问题，只是如果我需要再次为方法做别名，它会进入无限循环。 我想要一些更像super的东西，我可以根据需要多次扩展它，并且每个扩展名都使用alias作为其父级。
另一种方法是使用未绑定的方法：
class A original_test = instance_method(:test) define_method(:test) do puts "Log Message!" original_test.bind(self).call end end class A original_test = instance_method(:test) counter = 0 define_method(:test) do counter += 1 puts "Counter = #{counter}" original_test.bind(self).call end end irb> A.new.test Counter = 1 Log Message! #=> #.... irb> A.new.test Counter = 2 Log Message! #=> #.....
这样做的好处是，它不会使用其他方法名称污染命名空间，并且如果您想要创建类方法add_logging或者您拥有什么，则相当容易抽象。
class Module def add_logging(*method_names) method_names.each do |method_name| original_method = instance_method(method_name) define_method(method_name) do |*args,&blk| puts "logging #{method_name}" original_method.bind(self).call(*args,&blk) end end end end class A add_logging :test end
或者，如果你想能够用很多锅炉板做一堆方面，你可以写一个方法来编写方面添加方法！
class Module def self.define_aspect(aspect_name, &definition) define_method(:"add_#{aspect_name}") do |*method_names| method_names.each do |method_name| original_method = instance_method(method_name) define_method(method_name, &(definition[method_name, original_method])) end end end # make an add_logging method define_aspect :logging do |method_name, original_method| lambda do |*args, &blk| puts "Logging #{method_name}" original_method.bind(self).call(*args, &blk) end end # make an add_counting method global_counter = 0 define_aspect :counting do |method_name, original_method| local_counter = 0 lambda do |*args, &blk| global_counter += 1 local_counter += 1 puts "Counters: global@#{global_counter}, local@#{local_counter}" original_method.bind(self).call(*args, &blk) end end end class A def test puts "I'm Doing something..." end def test1 puts "I'm Doing something once..." end def test2 puts "I'm Doing something twice..." puts "I'm Doing something twice..." end def test3 puts "I'm Doing something thrice..." puts "I'm Doing something thrice..." puts "I'm Doing something thrice..." end def other_tests puts "I'm Doing something else..." end add_logging :test, :test2, :test3 add_counting :other_tests, :test1, :test3 end
第一选择：子类而不是覆盖：
class AWithLogging < A\ def test puts "Log Message!" super end end
第二选择：更仔细地命名您的orig方法：
class A # with logging! alias_method :test_without_logging, :test def test puts "Log Message!" test_without_logging end end
然后另一个方面使用不同的原始名称：
class A # with frobnication! alias_method :test_without_frobnication, :test def test Frobnitz.frobnicate(self) test_without_frobnication end end