Creating records in specs can be so fast that two records created instantly after one another might have the same created_at timestamp (especially since those timestamps don't have an indefinitely high resolution). When ordering lists by timestamps, you should therefore always include a final order condition using the primary key of the table.

class Photo < ActiveRecord::Base
  scope :by_date, -> { order('created_at DESC, id DESC') }
end

Photo.by_date

Remember to include the id field in the database index.

Thomas Klemm

Say thanks9

Last edit

Over 1 year ago

Michael Leimstädtner

License

Source code in this card is licensed under the MIT License.

Delivering Carrierwave attachments to authorized users only

Preparation

To attach files to your records, you will need a new database column representing the filename of the file. To do this, add a new migration (rails g migration <name>) with the following content:

class AddAttachmentToNotes...

PostgreSQL: How to change attributes of a timestamp

It's generally not trivial to change a datetime's seconds, minutes, etc in SQL. Here is how it works when speaking PostgreSQL.

Consider you have a timestamp column whose seconds you want to zero:

SELECT born_at FROM users;
       born_at...

Convert colorspace of images attached with Paperclip

has_attached_file(
  :avatar,
  :styles => { :large => "300x300", :small => "100x100" },
  :convert_options => { all => "-colorspace RGB" }
)

CSS: Matching against attributes and their values (or parts of them)

You probably know that you can use CSS selectors to match against elements and their attributes, such as:

a[title] { /* any <a> that has a "title" */ }
a[data-fancy="true"] { /* any <a> that has their "data-fancy" attribute set to "true" *...

Posted by Thomas Klemm to makandra dev (2014-10-24 12:08)

Deterministic ordering of records by created_at timestamp

Related cards:

Preparation