How to drop all tables in PostgreSQL
To remove all tables from a database (but keep the database itself), you have two options.
Option 1: Drop the entire schema
You will need to re-create the schema and its permissions. This is usually good enough for development machines only.
DROP SCHEMA public CASCADE;
CREATE SCHEMA public;
GRANT ALL ON SCHEMA public TO postgres;
GRANT ALL ON SCHEMA public TO public;
Applications usually use the "public" schema. You may encounter other schema names when working with a (legacy) application's database.
Note that f...
Merging two arbitrary ActiveRecord scopes
Rails 3+ allows you to join two scopes from arbitrary sources by calling the merge method:
scope1 = User.where(:email => 'foo@bar.com')
scope2 = User.where(:first_name => 'hans')
merged_scope = scope1.merge(scope2)
merged_scope.to_a will now trigger a query for the combined scope chain:
SELECT `users`.* FROM `users` WHERE `users`.`email` = 'foo@bar.com' AND `users`.`first_name` = 'hans'
If you are joining two models, you can also [merge scopes for different models](http://blog.thefrontiergroup.com.au/2011/03/composing...
How to overwrite and reset constants within Cucumber features
In order to save the original value of a constant, set the new value and restore the old value after a scenario was completed, you can use the following helper. It takes care of saving the old constant value, setting the new one without throwing warnings and resets the value with an After hook.
This module also enables you to introduce new global constants.
Since these newly defined constants do not have any value to be reset to,
they simply are deleted (remove_const) once the respective Cucumber step finishes.
You can copy the file at...
What collapsing margins are, how they work and when margins do not collapse
What collapsing margins are
Imagine you have 2 HTML boxes. The first one has a margin-bottom of let's say 30px and the second one a margin-top of 20px. After rules of collapsing margins have been applied we have a margin of 30px (not 50px) between these two boxes (see this article for an illustration) . This is because no addition of both margins takes place but the maximu...
Geordi hints
Reminder of what you can do with Geordi.
Note: If you alias Geordi to something short like g, running commands gets much faster!
Note: You only need to type the first letters of a command to run it, e.g. geordi dep will run the deploy command.
geordi deploy
Guided deployment, including push, merge, switch branches. Does nothing without confirmation.
geordi capistrano
Run something for all Capistrano environments, e.g. geordi cap deploy
geordi setup -t -d staging
When you just c...
Copying validation errors from one attribute to another
When using virtual attributes, the attached trait can be useful to automatically copy errors from one attribute to another.
Here is a typical use case where Paperclip creates a virtual attribute :attachment, but there are validations on both :attachment and :attachment_file_name. If the form has a file picker on :attachment, you would like to highlight it with errors from any attribute:
class Note < ActiveRecord::Base
has_attached_file :attachment
validates_attachment_presenc...
Cucumber Factory: How to assign polymorphic associations
Cucumber factory supports polymorphic associations out of the box. Just keep in mind that you need to use named associations for this purpose.
class Person < ApplicationModel
has_many :buildings, inverse_of: :owner
end
class Company < ApplicationModel
has_many :buildings, inverse_of: :owner
end
class Building < ApplicationModel
belongs_to :owner, optional: true, polymorphic: true
end
Works
Given there is a person with the name "Nice person"
And there is a buildin...
The Easiest Way to Parse URLs with JavaScript
A very clever hack to parse a structured URL object is to create a <a> element and set its href to the URL you want to parse.
You can then query the <a> element for its components like schema, hostname, port, pathname, query, hash:
var parser = document.createElement('a');
parser.href = 'http://heise.de/bar';
parser.hostname; // => 'heise.de'
pathname = parser.pathname; // => '/bar'
if (pathname[0] != '/')
pathname = '/' + pathname // Fix IE11
One advantag...
How to combine "change", "up", and "down" in a Rails migration
Rails migrations allow you to use a change method whose calls are automatically inverted for the down path. However, if you need to some path-specific logic (like SQL UPDATE statements) you can not define up and down methods at the same time.
If you were to define define all 3 of them, Rails would only run change and ignore up and down. However, Rails 4+ features a helper method called reversible:
class MyMigration < ActiveRecord::Migration
def...
Javascript: Don't throw exceptions from async functions
TLDR: A function is hard to use when it sometimes returns a promise and sometimes throws an exception. When writing an async function, prefer to signal failure by returning a rejected promise.
The full story
When your function returns a promise ("async function"), try not throw synchronous exceptions when encountering fatal errors.
So avoid this:
function foo(x) {
if (!x) {
throw "No x given"
} else
return new Promise(function...
Regular tasks for long-running projects
When projects run for many years, they require special regular maintenance to stay fresh. This kind of maintenance is usually not necessary for small or quick projects, but required to keep long-running projects from getting stale.
You should be able to fit this into a regular development block.
Quarterly
Check which libraries need updating
As time goes by, libraries outdate. Check your software components and decide if any of it needs an update. Your main components (e.g. Ruby, Rails, Angular) should always be reasonably up to ...
Building web applications: Beyond the happy path
When building a web application, one is tempted to claim it "done" too early. Make sure you check this list.
Different screen sizes and browsers
Desktops, tablets and mobile devices have all different screen resolutions. Does your design work on each of them?
- Choose which browsers to support. Make sure the page looks OK, is usable and working in these browsers.
- Use @media queries to build a responsive design
- If you do not suppo...
Don't forget: Automatically remove join records on has_many :through associations
Bad
# Given the following models
class Image < ActiveRecord::Base
has_many :album_image
has_many :albums, through: :album_images
end
class Album < ActiveRecord::Base
has_many :album_image
has_many :images, through: :album_images
end
# Join model
class AlbumImage < ActiveRecord::Base
belongs_to :album
belongs_to :image
end
Destroying a record in this setup will only remove the record itself, and leave orphaned join records behind.
image = Image.last
image.destroy # removes only the `image` record,
...