Virtual attributes and mass-assignment

问题:

developers! I can't understand next situation

For Example I have model

class Pg::City < ActiveRecord::Base
   belongs_to :country  
   #virtual accessors
   attr_accessor :population
   #attr_accessible :city, :isdisabled,  :country_id

end

I can use code like this:

c = Pg::City.new({:population=>1000})
puts c.population
1000

But if I uncomment attr_accessible code above throw warning

WARNING: Can't mass-assign protected attributes: population

How can I use virtual attributes for mass-assigmnment together with model attributes? Thanks!

回答1:

Using attr_accessor to add a variable does not automatically add it to attr_accessible. If you are going to use attr_accessible, then you will need to add :population to the list:

attr_accessor :population
attr_accessible :city, :isdisabled, :country_id, :population