The ancestry gem allows you to easily use tree structures in your Rails application.

There is one somewhat unobvious pitfall to it: its way of applying the orphan_strategy which defines how it handles children of an object going to be destroyed.

What's this all about?

In many cases you might want to disallow destruction if there are any child nodes present. The restrict strategy does the trick but raises an exception when destroy is called:
has_ancestry :orphan_st...

If you need to look at the list of methods that are called upon certain events (like before/after saving etc), do this:

Model._save_callbacks.select {|cb| cb.kind == :before}.map{ |c| c.instance_variable_get :@filter }

Rails 2

User.after_save_callback_chain

To look at the method names only, you could do something like that:

User.after_save_callback_chain.collect(&:method)

If you get an ActiveRecord::RecordNotSaved error, a method inside one of your model's callback chains (before_save etc) possibly returned false.

This commonly happens when you have a method setting attributes and the last one is a boolean set to false (as the value of the last statement is returned). Fix this by simply calling true at the end of such methods:

def hide
  self.visible = false
  true
end

Note that nil won't cause this behavior. Thus, you can use an if without problems -- if you are not returning fal...

When you do tags with acts-as-taggable-on and want to preload associated tags, you can do so with

TaggedModel.scoped(:include => :tag)

Note however that this will only prevent tagged_model.tags from hitting the database. Using tagged_model.tag_list does not use the preloaded association.

If you want to see how long your database queries actually take, you need to disable MySQL's query cache. This can be done globally by logging into a database console, run

SET GLOBAL query_cache_type=OFF;

and restart your rails server.

You can also disable the cache on a per query basis by saying

SELECT SQL_NO_CACHE * FROM ...

You also probably want to disable Rails internal (per-request) cache. For this, wrap your code with a call to ActiveRecord::Base.uncached. For example, as an around_filter:

d...

Hooks lets you define hooks declaratively in your ruby class. You can add callbacks to your hook, which will be run as soon as you run the hook.

Note that you should disable the Java plug-in in your browsers after installation.

Ubuntu >= 12.04

Java 11

sudo apt install openjdk-11-jre-headless

Java 10

sudo add-apt-repository ppa:linuxuprising/java
sudo apt-get update
sudo apt-get install oracle-java10-installer

Java 8

You probably want to get rid of OpenJDK (which is installed by default and leads to bad RubyMine performance):

...

Rails 2

You can use

record.send(:update_without_callbacks)

or

record.send(:create_without_callbacks)

This can be used as a lightweight alternative to machinist's make or FactoryGirl's create, when you just need objects in the database but don't care about any callbacks or validations. Note that create_without_callbacks does not return the object, so you might want to do

record = Record.new.tap(&:create_without_callbacks)

Rails 3

Rails 3 no longer comes with update_without_callbacks or `crea...

Find conditions for scopes can be given either as an array (:conditions => ['state = ?', 'draft']) or a hash (:conditions => { 'state' => 'draft' }). The later is nicer to read, but has horrible security implications in some versions of Ruby on Rails.

Affected versions

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_presence :a...

Use like this:

power-rake db:migrate VERSION=20100913132321

By default the environments development, test, cucumber and performance are considered. The script will not run rake on a production or staging environment.

This script is part of our geordi gem on github.

There are many different methods that allow mapping an Array to a Hash in Ruby.

Array#to_h with a block (Ruby 2.6+)

You can call an array with a block that is called with each element. The block must return a [key, value] tuple.

This is useful if both the hash key and value can be derived from each array element:

users = User.all
user_names_by_id = users.to_h { |user| [user.id, user.name] }

{
  1 => "Alice",
  2 => "Bob"
}

Array#to_h on an array of key/value tuples (Ruby 2.1+)

Converts an Array ...

When Paperclip attachments should only be downloadable for selected users, there are three ways to go.
The same applies to files in Carrierwave.

1. Deliver attachments through Rails

The first way is to store Paperclip attachments not in the default public/system, but in a private path like storage inside the current release. You should prefer this method when dealing with sensitive data.

Make ...

In modern Rails versions you can also use ActiveRecord's pluck method.

User.active.pluck(:id)
=> [1, 5, 23, 42]

If you are plucking from the id column in particular you can also say:

User.active.ids
=> [1, 5, 23, 42]

For a DISTINCT selection, use distinct on your scope (not the resulting array).

Article.distinct.pluck(:state)
...

When you load a record with find options that have SQL fragments in :select or :joins, ActiveRecord will make that record read-only. This is a protective measure by Rails because such a record might have some additional attributes that don't correspond to actual table columns.

You can override that precaution by appending :readonly => false to affected find options or scope options.

This post explains, in some detail, how we will implement a nice performance boost for Rails developers. Understanding the details might help gain the full benefits of the optimization, but you will gain some benefits even if you have no idea how it works.

The state_machine gem ships with a scope with_state. This scope has some problems in complex queries or scope chains.

Use this instead:

named_scope :having_state, lambda { |*state_or_states|
  state_or_states = Array.wrap(state_or_states).map(&:to_s)
  { :conditions => [ 'articles.state IN (?)', state_or_states ] }
}

If you want a scope with hash options (with the side effects you should know about):

named_scope :having_st...

Sometimes you want to fetch associations for an ActiveRecord that you already loaded, e.g. when it has deeply nested associations.

Edge Rider gives your models a static method preload_associations. The method can be used to preload associations for loaded objects like this:

class UsersController < ApplicationController
  def show
    @user = User.find(params[:id])
    @user.preload_associations(threads: { posts: :author }, messages: :sender)
  end
end

The attached initializers re...

When you need to add a event listener to hundreds of elements, this might slow down the browser.

An alternative is to register an event listener at the root of the DOM tree (document). Then wait for events to bubble up and check whether the triggering element (event.target) matches the selector before you run your callback.

This technique is called event delegation.

Performance considerations

Because you only register a single listener, registering is ...

You can write regular expressions some different ways, e.g. /regex/ and %r{regex}. For examples, look here.

Remember that it is always a good idea to match a regex visually first.

Characters

Literal Characters

[ ] \ ^ $ . | ? * + ( )

Character Classes

[ae]            matches a and e, e.g. gr[ae]y => grey or gray => but NOT graay or graey
[0-9]  ...

jamesgolick / resource_controller at Github

module ResourceController
  module Actions
    
    def index
      load_collection
      before :index
      response_for :index
    end
    
    def show
      load_object
      before :show
      response_for :show
    rescue ActiveRecord::RecordNotFound
      response_for :show_fails
    end

    def create
      build_o...