#101 オリジナルの作成日時，フォームにフィールド追加

backend/app/models/post.rb

@@ -15,6 +15,8 @@ class Post < ApplicationRecord
            foreign_key: :target_post_id
   has_one_attached :thumbnail
 
+  validate :validate_original_created_range
+
   def as_json options = { }
     super(options).merge({ thumbnail: thumbnail.attached? ?
                                       Rails.application.routes.url_helpers.rails_blob_url(
@@ -49,4 +51,20 @@ class Post < ApplicationRecord
                      filename:      'resized_thumbnail.jpg',
                      content_type:  'image/jpeg')
   end
+
+  private
+
+  def validate_original_created_range
+    f = original_created_from
+    b = original_created_before
+    return if f.blank? || b.blank?
+
+    f = Time.zone.parse(f) if String === f
+    b = Time.zone.parse(b) if String === b
+    return if !(f) || !(b)
+
+    if f >= b
+      errors.add :original_created_before, 'オリジナルの作成日時の順番がをかしぃです．'
+    end
+  end
 end