Rails: Ignoring non-existant attributes passed to create()

Question

I have the following Rails model:

class CreateFoo < ActiveRecord::Migration
  def self.up
    create_table :foo do |t|
      t.string :a
      t.string :b
            


        

Answer 1

You can use Hash#slice and column_names method exists also as class method.

hash = {a: 'some', b: 'string', c: 'foo', d: 'bar'}
Foo.create(hash.slice(*Foo.column_names.map(&:to_sym)))

Answer 2

I use this frequently (simplified):

params.select!{|x| Model.attribute_names.index(x)}
Model.update_attributes(params)

Answer 3

I think using the attr_accessible method in the model class for Foo would achieve what you want, e.g.,:

class Foo < ActiveRecord::Base

  attr_accessible :a, :b, :c

  ...
end

This would allow the setting/updating of only those attributes listed with attr_accessible.

Answer 4

I found a solution that works fairly well, and is ultimately a combination of the above options. It allows for invalid params to be passed (and ignored), while valid ones are mapped correctly to the object.

def self.initialize(params={})
  User.new(params.reject { |k| !User.attribute_method?(k) })
end

Now rather than calling User.new(), call User.initialize(). This will "filter" the correct params fairly elegantly.

Answer 5

I came up with a solution that looks like this, you might find it helpful:

def self.create_from_hash(hash)
  hash.select! {|k, v| self.column_names.include? k }
  self.create(hash)
end

This was an ideal solution for me, because in my case hash was coming from an ideal data source which mirrored my schema (except there were additional fields).

Answer 6

I just had this exact problem upgrading to Rails 3.2, when I set:

config.active_record.mass_assignment_sanitizer = :strict

It caused some of my create! calls to fail, since fields that were previously ignored are now causing mass assignment errors. I worked around it by faking the fields in the model as follows:

attr_accessor   :field_to_exclude
attr_accessible :field_to_exclude