ActiveRecord#find needs an id even when to_param/from_param has an override

active_record_find_and_from_param.rb

# couple of problems
# 1. the name to_param is not domain specific. it is to uniquely specify
# the record in urls and such
# 2. find does not work seamlessly with to_param

# read comments at http://apidock.com/rails/ActiveRecord/Base/to_param

class PaymentOld < ActiveRecord::Base
  attr_accessible :amount, :desc

  def to_param
    desc
  end

  def self.from_param(name)
    find_by_desc name
  end
end

class Payment < ActiveRecord::Base
  attr_accessible :amount, :desc

  def to_param
    "#{id}-desc"
  end

  def self.from_param(name)
    find_by_desc name.split('-').second
  end
end

p = PaymentOld.create! amount: 100, desc: "first"
p.to_param #first
PaymentOld.from_param(p.to_param) #got it
PaymentOld.find(p.to_param) #fails 
# ActiveRecord::RecordNotFound: Couldn't find PaymentOld with id=first
# read comments at http://apidock.com/rails/ActiveRecord/Base/to_param

# but if to_param appends id to to_param then it works
# as find searches for an id at the start and ignores all

p = Payment.create! amount: 100, desc: "first"
p.to_param #1-first Note that 'id' is appended
Payment.from_param(p.to_param) #got it
Payment.find(p.to_param) # success
param = p.to_param
p.desc = "second"
p.save!
#still works even though the record does not have that desc
Payment.find(param) 

created an issue at, rails/rails#7092