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.

When you're getting this error, one possibility is that you've created a select field for an association instead of the associated object's id. Example:

form.select :unit, Unit.for_select

will be expected to deliver a real Unit object, whereas

form.select :unit_id, Unit.for_select

will make Rails typecast the String value from the select field to the unit's ID.

Ancestry is a gem/plugin that allows the records of a Ruby on Rails ActiveRecord model to be organised as a tree structure (or hierarchy). It uses a single, intuitively formatted database column, using a variation on the materialised path pattern. It exposes all the standard tree structure relations (ancestors, parent, root, children, siblings, descendants) and all of them can be fetched in a single sql query. Additional features are STI support, named_scopes, depth caching, depth constraints, easy migration from older plugins/gems, integrit...

In Rails, you can very easily send emails with HTML and plaintext bodies.

However, if you're trying to debug those using your normal email account, you might be out of luck: For some reason, Exchange servers will simply throw away the plaintext part of your mail, and just save the html part.

There are many solutions, but a very concise one is this:

hash.merge!(hash) do |key, old_value, new_value|
  # Return something
end

The block of merge! will be called whenever a key in the argument hash already exists in the base hash. Since hash is updated with itself, each key will conflict and thus allow you to modify the value of each key to whatever you like (by returning old_value you'd get the behavior of Rails' reverse_merge!, by re...

Unicorn allows you to specify the maximum number of workers. In development this could be useful if you use a debugger, but do not want to overflow the console with other request like from ActionCable. Then just set the maximum number of workers to 1 and the other requests have to wait.

UNICORN_WORKERS=1 rails server

In the ruby shell (IRB) and rails console the return value of the previous command is saved in _ (underscore). This might come in handy if you forgot to save the value to a variable and further want to use it.

Example:

irb(main):001:0> 1 + 2
=> 3
irb(main):002:0> _
=> 3
irb(main):003:0> a = _
=> 3

yaml4r is a juxtaposition of yaml documents and their Ruby couterpart. Thus, it does a great job as YAML-doc, e.g. when writing Rails locale files. Did you know that ...

• << is a merge key (similar to & in SASS)
• there are variables, called aliases. Definition: &alias Some content, usage: *alias.

Caveats

Specifying a key twice does not merge the sub keys, but override the first definition, e.g.

de:
  car: # overridden
    door: Tür
 ...

In order to prevent the browser from asking whether to remember the password, give a form an autocomplete attribute with the value off:

<form "/session" method="post" autocomplete="off">
  ...
</form>

Rails example

form_for @model, :html => { :autocomplete => "off" } do |form|

Under certain circumstances gettext_i18n_rails will hit a near-infinite loop. This occured in Rails 2.3.5 with Haml 3.0.18 and fast_gettext 0.5.10.

gettext_i18n_rails's Haml-Parser compiles the Haml code and delegates the parsing to ruby_parser. Unfortunately, ruby_parser appears to be confused when a string contains both escaped chars (that is, any unicode characters as ndash, umlauts etc.) and #{} blocks, which makes it extremely slow.

The easiest "solution" we came up with was to replace all occurrences of UTF-8 chars wi...

TruffleRuby is an experimental Ruby implementation that tries to achieve ~10x performance over MRI.

This has been on our radar for a while. They seem to have made significant progress running Rails, reducing start-up time and becoming runtime-independent of the JVM.

Also see [Running Optcarrot, a Ruby NES emulator, at 150 fps with the GUI!](https://eregon.me/blog/2016/11/28/optcarrot.htm...

If you have a file that looks like a precompilation fingerprint, the Rails asset pipeline will not see it. So don't have filenames like this:

8e21264d-f678-4005-b90c-8d8288a0d179.ttf

Don't say is_a?(ActiveRecord::NamedScope::Scope) because that is no longer true in Rails 3 and also doesn't match unscoped ActiveRecord classes themselves (which we consider scopes for all practical purposes).

A good way is to say this instead:

object.respond_to?(:scoped)

If you want to update some records with boolean fields in a migration, always remember to set your values with field=#{quoted_true} and field=#{quoted_false}. The Rails methods quoted_false and quoted_true return the correct boolean representations for your database.

Usually, Cucumber feature files live in features/. When you group them in sub directories, make sure to add -r features to the standard Cucumber options.

In Rails apps, Cucumber options are likely to be stored in config/cucumber.yml.

When you include a non-existing Javascript file, you probably won't notice it during development. But with caching active (on production or staging) Rails will write an empty all.js file without complaining.

Free Bootstrap theme resembling Material Design.

Bootswatch offers Sass and Less files, so the theme can easily be integrated into your usual Rails application.

Implements only Bootstrap features which means that some Material stuff is missing, but also that you can easily use or replace the theme.
Does not come with extra JavaScript; some effects like button click ripples are implemented via CSS.

Also check out their other themes which can be used in a similar fashion.

Use Traim to build a RESTful API for your ActiveRecord models with very little code.

Traim assumes your API resources will map 1:1 to your ActiveRecord models and database tables. This assumption usually falls apart after a few months into a project, so be ready to replace your Traim API with something more expressive afterwards.

Traim outputs a Rack application which you can either serve standalone or mount into your Rails app.

This finally works:
User.any_instance.should_receive(...)
as does
User.any_instance.stub(...)

Note: You won't have RSpec 2.6 if you're still working on Rails 2.

This is what worked for me in a Rails 4:

# JSON data as first argument, then parameters
patch :update, { some: 'data' }.to_json, id: id, format: :json

Ruby 1.9.2 is very slow when loading files, especially starting Rails servers or running specs takes forever.

Do yourself a favor and upgrade to 1.9.3.

This will give you the string that appears most often in an array:

names = %w[ foo foo bar bar bar baz ]
names.group_by(&:to_s).values.max_by(&:size).try(:first)
=> "bar"

This is very similar to the linked StackOverflow thread, but does not break on empty arrays.

Note that try is provided by ActiveSupport (Rails). You could explicitly load activesupport or use andand on plain Ruby.