Why is Rails setting my attribute to nil on create? - ruby-on-rails

Question

Ruby 2.2.0 on Rails 4.2.2
I'm attempting to write a custom date validator (that is going to be expanded to handle some other cases once I get this part working), but right now it's failing to appropriately validate (and return false) on strings - it doesn't even run. It seems that rails is completely ignoring the date_ended value when it's set to a string. When I try the same test except with an integer it correctly validates and fails that validation. If I don't allow nil values, the validator correctly prevents record creation on a string value, but only because it rejects the nil value. Any and all suggestions are appreciated.
The same exact problem exists for date_started.
Edit: I've confirmed that the validation is failing on the second expectation and not the first validation by double-checking that CommitteeMember.count is 0 before the first expectation.
CommitteeMember:
class CommitteeMember < ActiveRecord::Base
belongs_to :committee
belongs_to :member
validates :committee_id, presence: true
validates :member_id, uniqueness: { scope: :committee_id }, presence: true
validates :date_started, date: true, allow_nil: true
validates :date_ended, date: true, allow_nil: true
end
schema.rb relevant lines:
create_table "committee_members", force: :cascade do |t|
t.integer "committee_id", null: false
t.integer "member_id", null: false
t.date "date_started"
t.date "date_ended"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
DateValidator (custom validator):
(note the printed value in the middle)
class DateValidator < ActiveModel::EachValidator
def validate_each(record, attribute, value)
puts "Validating #{value}"
unless value.kind_of?(Date)
record.errors[attribute] << "must be of type date"
end
end
end
CommiteeMember relevant spec:
(note the printed value in the middle)
it 'should fail with a string for date_ended' do
expect(CommitteeMember.count).to eq(0)
CommitteeMember.create!(member_id: 1, committee_id: 1, date_ended: "S")
ap CommitteeMember.first
expect(CommitteeMember.count).to eq(0)
end
Spec Output:
$ rspec spec/models/committee_member_spec.rb
......#<CommitteeMember:0x00000007d1f888> {
:id => 1,
:committee_id => 1,
:member_id => 1,
:date_started => nil,
:date_ended => nil,
:created_at => Tue, 11 Aug 2015 19:22:51 UTC +00:00,
:updated_at => Tue, 11 Aug 2015 19:22:51 UTC +00:00
}
F
Failures:
1) CommitteeMember validations should fail with a string for date_ended
Failure/Error: expect(CommitteeMember.count).to eq(0)
expected: 0
got: 1
(compared using ==)
# ./spec/models/committee_member_spec.rb:52:in `block (3 levels) in <top (required)>'
Finished in 0.54864 seconds (files took 2.43 seconds to load)
7 examples, 1 failure
Failed examples:
rspec ./spec/models/committee_member_spec.rb:48 # CommitteeMember validations should fail with a string for date_ended

Answer 1

Since the attributes are date attributes, Rails automatically parses any values that you attempt to assign. If it cannot parse as a date, it will leave the value as nil, e.g. in the console:
c = CommitteeMember.new
c.date_started = 'S'
=> "S"
c.date_started
=> nil
In fact, Rails will actually parse a string into a Date:
c.date_started = '2016-1-1'
=> "2016-1-1"
c.date_started
=> Fri, 01 Jan 2016
c.date_started.class
=> Date
This means that you don't need to validate that your date fields are dates at all, because Rails won't store them otherwise. Instead, just validate that they exist:
validates_presence_of :date_started, :date_ended