我正在尝试编写一个库,该库将以编程方式向ActiveRecord模型添加around_update
/around_destroy
回调。
因此,一个常规模型会是这样的,并且它可以按预期工作:
class User < ActiveRecord::Base
around_update :test_update
def test_update
Rails.logger.debug "test_update"
yield
Rails.logger.debug "Finished test_update"
end
end
u=User.last
u.name = 'something'
u.save
######### output (as expected):
# test_update
# Finished test_update
我的小图书馆(显然只是骨架)看起来是这样的:
# A module for creating around callbacks in a model
module Piddle
module TimelineFor
def self.included(klass)
klass.send(:extend, ClassMethods)
end
module ClassMethods
def timeline_for(event, opts={})
method_name = :"timeline_for_#{event.to_s}"
define_method(method_name) do |&block|
Rails.logger.debug method_name.to_s
yield block
Rails.logger.debug "After yield in #{method_name.to_s}"
end
send(:around_update, method_name)
end
end
end
end
它定义了一个timeline_for方法,该方法应添加timeline_for_update方法,并使其成为around_update事件的回调。我想使用的用户模型是:
# second version of the User model using Piddle to create the callback
require 'piddle/piddle'
class User < ActiveRecord::Base
include Piddle::TimelineFor
timeline_for :update
end
u=User.last
u.name = 'gfgfhfhfgh'
u.save
在输出中,我看到
timeline_for_update
LocalJumpError: no block given (yield)
from /vagrant/lib/piddle/piddle.rb:13:in `block in timeline_for'
第一个输出行表示正在调用该方法,但没有传入块
有什么想法或替代实施方案吗?
问题是,如果从define_method
调用yield
,ruby会将其解释为试图屈服于传递给timeline_for
的(不存在的)块,而不是块轨道通过timeline_for_foo
你有block
被传递给你,所以你可以称之为:
def timeline_for event
method_name = "timeline_for_#{event}"
define_method method_name do |&block|
ActiveRecord::Base.logger.debug "before #{method_name} yield"
block.call
ActiveRecord::Base.logger.debug "after #{method_name} yield"
end
send :around_update, method_name.to_sym #must use a symbol here
end
如果你想定义这样的东西。看看积极支持关注的问题。
我认为您需要在类上调用around过滤器,而不是在定义本身中使用send:
http://apidock.com/rails/ActiveSupport/Concern