In this example we assume that not only the storage gem changes but also the file structure on disc.
Part A: Create a commit which includes a script that allows you to copy the existing file to the new file structure.
Part B: Create a commit which removes all paperclip logic and replace it with the same code you used in the first commit
Here are some implementation details you might want to reuse:
Masonry is a famous library to dynamically arrange a grid of items that have different aspect ratio, like horizontal and vertical images.
Colcade is an alternative masonry-layouting library, developed by the same developer, but with a more modern approach.
It is said to have better performance while being smaller and having no dependencies. It automagically detects jQuery and defines a jQuery initializer, if present.
However, it offers [a few less features](https:...
Geordi's cucumber command has a --rerun option that reruns failing tests the given number of times. Usage:
geordi cucumber path/to/features --rerun=2
geordi cucumber path/to/features -r2
Cucumber will save a file tmp/parallel_cucumber_failures.log containing the filenames and line number of the failed scenarios after a full test run. Normally you can say cucumber -p rerun (rerun is a profile defined by default in config/cucumber.yml) to rerun all failed scenarios.
Here are a few al...
If you use transactional_fixtures or the database_cleaner gem with strategy :transaction, after_commit callbacks will not be fired in your tests.
Rails 5 has a fix for this issue and no further action is needed.
Add the gem test_after_commit to your test group in the Gemfile and you are done. You don't need to change the database strategy to deletion (wh...
If validations failed for a record, and you want to find out if a specific validation failed, you can leverage ActiveModel's error objects.
You rarely need this in application code (you usually just want to print error messages), but it can be useful when writing tests.
As an example, consider the following model which uses two validations on the email attribute.
class User < ApplicationRecord
validates :email, presence: true, uniqueness: true
end
Let's assume we have a blank user:
user = Us...
We want to keep a changelog for all gems we maintain. There are some good practices for writing a changelog that adds value, please stick to these.
A changelog is a file which contains a curated, chronologically ordered list of notable changes for each version of a project.
To make it easier for users and...
Most forms have a single submit button that will save the record when pressed.
Sometimes a form needs additional submit buttons like "accept" or "reject". Such buttons usually attempt a state transition while updating the record.
To process a form with multiple buttons, your server-side code will need to know which button was pressed. To do so you can give each submit button a different [formaction] attribute. This will override the ...
If you need to run a program on a remote machine (e.g. to your office PC) with a graphical UI (and you trust the remote machine), you can use SSH X-Forwarding. I sometimes use this to connect to a virtual machine installed on my work PC from my home office.
To use X forwarding, when connecting to the remote machine, and add -X to the ssh call. Now, when you start a program with a UI (e.g. virtualbox) in that SSH session, a window will open on your local machine. It will not be particularly ...
Migrating data from a legacy into a new system can be a surprisingly large undertaking. We have done this a few times. While there are significant differences from project to project, we do have a list of general suggestions.
Before you start, talk to someone who has done it before, and read the following hints:
Before any technical considerations, you need to understand the old system as best as possible. If feasible, do not only look at its API, or database, or frontend, but let a user of the old system sho...
Google Chrome has a subtle rendering bug that hits me once in a while. It usually occurs in sliders with HTML content.
When a slider contains a composited[1] element, the element will overlap any other element when sliding, being rendered as frontmost element. After the slider has settled, stacking order jumps back to normal.
It seems like Chrome is doing its compositing wrong. This doesn't happen in Firefox.
The issue only occurs if:
Having a unique selector for an element is useful to later select it from JavaScript or to update a fragment with an Unpoly.
Haml lets you use square brackets ([]) to generate a unique class name and ID from a given Ruby object. Haml will infer a class attribute from the given object's Ruby class. It will also infer an id attribute from the given object's Ruby class and #id method.
This is especially useful with ActiveRecord instances, which have a persisted #id and will hence **generate the same selector o...
Rails has a default mechanism to store the session in the CookieStore. This is a cookie which holds the entire user session hash in the browser. This cookie is serialized, encoded with base64, and signed.
Devise uses this CookieStore. To track a users session, a salt is stored in the session ...
When you need to store structured data (like Ruby hashes) in a single database column with ActiveRecord, a simple way is to use PostgreSQL's jsonb columns. ActiveRecord will automatically serialize and deserialize your Hash to and from JSON, and you can index JSON paths for fast reads.
As an alternative, ActiveRecord::Store offers a way to store hashes in a single database column. This card will show you how to migrate those hashes in an ActiveRecord::Migration by example:
...
If your rails application is unable to send mails, it might be useful to debug your settings using the rails console. Here is a snippet that shows the current settings and lets you send a test mail directly from the console:
mailer = ActionMailer::Base.new
# check settings:
mailer.delivery_method # -> :smtp
mailer.smtp_settings # -> { address: "localhost", port: 25, domain: "localhost.localdomain", user_name: nil, password: nil, authentication: nil, enable_starttls_auto: true }
# send mail:
mailer.mail(from: 'sender@example.com', ...
When you have a large PG database, you may want to find out which tables are consuming the most disk space.
You can easily check this using the following SQL statement from the PostgreSQL wiki.
SELECT nspname || '.' || relname AS "relation",
pg_size_pretty(pg_total_relation_size(C.oid)) AS "total_size"
FROM pg_class C
LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
WHERE nspname NOT IN ('pg_catalog', 'information_schema')
AND C.relkind <> 'i'
AND nspname !~ '^pg_toast'
ORDER BY pg_tot...
The attached article explains options you have to store the order of items in a database table.
The simplest solution of course is to use a position column. However the author explores some alternatives where you don't need to update multiple rows when you move a single item.
Boot partitions from installations prior to the 16.04 era are terribly small. When you install updates and encounter errors due to a full /boot partition, consider risizing it.
If you can't do the steps described below, ask someone experienced to help you out.
This has worked 100% so far. 1 out of 1 tries. ;)
When there is some unpartitioned space on your drive, increasing the size of /boot is actually very easy (even though the list below is rather long). It only takes a...
Don't sum up columns with + in a sql-query if NULL-Values can be present.
MySQL and PostgreSQL cannot sum up NULL values with the + value. The sum value will be NULL.
MySQL:
mysql> select 1 + 2 + 3;
+-----------+
| 1 + 2 + 3 |
+-----------+
| 6 |
+-----------+
1 row in set (0,00 sec)
mysql> select 1 + NULL + 3;
+--------------+
| 1 + NULL + 3 |
+--------------+
| NULL |
+--------------+
1 row in set (0,00 sec)
Postgres:
test_database=# select 1 + 2 + 3;
?column?
----------
6
(1 row)
t...
New features:
geordi delete_dumps [directory]Recursively search for files ending in *.dump and offer to delete those. When no argument is given, two default directories are searched for dump files: the current working directory and ~/dumps (for dumps created with geordi).
geordi drop_databasesDelete local MySQL/MariaDB and Postgres databases that are not whitelisted.
Authentication is handled via PAM for Postgres and MariaDB, via .my.cnf with fallback to mysql -p for MySQL. Different connection methods can be chosen via ...
You might have some trouble running a Rails LTS 2 app with MySQL 5.7.
If you don't want to hack Mysql 5.6 into your modern Ubuntu or use the MySQL sandbox, you might want to try MariaDB 10.x.
MariaDB 10.x should work with both old and new Rails applications.
[Switch to MariaDB](https://makandracards.com/makandra/468343-how-...
MySQL and MariaDB have an SQL mode setting which changes how MySQL behaves.
The SQL mode value is comprised of multiple flags like "STRICT_TRANS_TABLES, NO_ZERO_IN_DATE". Each flag activates or disables a particular behavior.
The default SQL mode varies widly between versions of MySQL and MariaDB. In general, more recent versions of MySQL and MariaDB have stricter settings than older versions, and MySQL has stricter settings than the more liberal MariaDB.
If your app explodes ...
Your default postgres user is named like your linux user. That default user has limited access privileges, which can cause issues such as:
Doing these things without a superuser will show a Postgres error or (in Ruby) raise PG::InsufficientPrivilege.
To do so, the application's PostgreSQL user must be a superuser. ...
mysql> SELECT @@global.version;
+------------------+
| @@global.version |
+------------------+
| 5.6.30 |
+------------------+
1 row in set (0,00 sec)
MySQL 5.6 Reference Manual says "BLOB and TEXT columns cannot have DEFAULT values".
If you want to run migrations in development here are two variants which might help. If you are not sure about the side effects (e.g. your application is broken when it doesn't set additional default values on application side, too...
If you want to make a screenshot of a website that works well in print or on a high-DPI screen (like Apple Retina displays), here is how you can capture a high-resolution screenshot.
You can do this without an addon:
CTRL + and CTRL - so it covers most of the window area. Leave a little padding on the left and right so...