Question

我从https://gist.github.com/scttnlsn/1295485开始，作为制作一个宁静的sinatra应用程序的基础。但是，我很难管理诸如

之类的路径的HaBTM关系

delete '/:objecttype/:objid/:habtm_type/:habtm_id'

我已经有了这个对象类型，这要归功于地图（按照这个要点），并且从数据库中提取正确的对象并且ID是直接的。但是，获取habtm的另一面并在objecttype上调用适当的方法来删除关系涉及将少量字符串转换为适当的对象和方法。

我提出了一个解决方案，但它使用了eval。我知道使用eval是邪恶的，这样做会腐蚀我的灵魂。有没有更好的方法来处理这个问题，或者我应该采取一些保护措施来保护代码并将其称为一天？

这是一个有效的，独立的，无sinatra的例子来展示我如何做eval：

require 'mongoid'
require 'pp'

def go
  seed

  frank = Person.find_by(name:"Frank")
  apt = Appointment.find_by(name:"Arbor day")

  pp frank
  really_a_sinatra_route(frank.id, "appointments", apt.id)
  frank.reload
  pp frank
end

def really_a_sinatra_route(id, rel_type,rel_id)
  # I use "model" in the actual app, but hardwired a person here to 
  # make a simpler example

  person  = Person.find_by(id: id)
  person.deassociate(rel_type,rel_id)
end

class Base
  def deassociate(relationship,did)
    objname = associations[relationship].class_name

    # Here's the real question... this scares me as dangerous. Is there 
    # a safer way to do this?
    obj = eval "#{objname}.find(did)"
    eval "#{relationship}.delete(obj)"
  end
end

class Person < Base
  include Mongoid::Document
  has_and_belongs_to_many :appointments

end

class Appointment < Base
  include Mongoid::Document
  has_and_belongs_to_many :persons
end

def seed
  Mongoid.configure do |config|
    config.connect_to("test_habtmexample")
  end
  Mongoid.purge!

  frank=Person.create(name:"Frank")
  joe=Person.create(name:"Joe")
  ccon = Appointment.create(name:"Comicon")
  aday = Appointment.create(name:"Arbor day")

  frank.appointments << ccon
  frank.appointments << aday
  ccon.persons << joe
  joe.reload
end

go

Answer 1

freenode上一位优秀的绅士帮助了我。这两个版本可以替换为：

obj= self.send(relationship.to_sym).find(did)
self.send(relationship.to_sym).delete(obj)

用类字符串按摩mongoid habtm

1 个答案: