诗歌rails之make a plugin

我们可以将Task类里的due_at_string这个虚拟属性的生成做成一个plugin:

ruby script/generate plugin stringify_time

ruby script/generate plugin stringify_time 

这将在vendor/plugins目录生成如下文件:

vendor
 plugins
  stringify_time
---init.rb
---install.rb
   lib
----stringify_time.rb
---Rakefile
---README
   tasks
   test
---uninstall.rb

vendor plugins stringify_time ---init.rb ---install.rb lib ----stringify_time.rb ---Rakefile ---README tasks test ---uninstall.rb 

我们来修改如下文件:
init.rb:

require 'stringify_time'

class ActiveRecord::Base
  extend StringifyTime
end

require 'stringify_time' class ActiveRecord::Base extend StringifyTime end 

stringify_time.rb:

module StringifyTime
  def stringify_time(*names)
    names.each do |name|
      define_method "#{name}_string" do
        read_attribute(name).to_s(:db)
      end

      define_method "#{name}_string=" do |time_str|
        begin
          write_attribute(name, Time.parse(time_str))
        rescue ArgumentError
          instance_variable_set("@#{name}_invalid", true)
        end
      end

      define_method "#{name}_invalid?" do
        instance_variable_get("@#{name}_invalid")
      end
    end
  end
end

module StringifyTime def stringify_time(*names) names.each do |name| define_method "#{name}_string" do read_attribute(name).to_s(:db) end define_method "#{name}_string=" do |time_str| begin write_attribute(name, Time.parse(time_str)) rescue ArgumentError instance_variable_set("@#{name}_invalid", true) end end define_method "#{name}_invalid?" do instance_variable_get("@#{name}_invalid") end end end end 

OK，我们可以来在Task类中使用我们刚才创建的插件了:

class Task < ActiveRecord::Base
  stringify_time :due_at

  def validate
    errors.add(:due_at, "is invalid") if due_at_invalid?
  end
end

class Task < ActiveRecord::Base stringify_time :due_at def validate errors.add(:due_at, "is invalid") if due_at_invalid? end end