Notes posted by foliosus

On destroying data

Reply to tvle83 and pgmcgee: the destructiveness of this method depends on your database. Some databases are better at converting between disparate types than others. For example, when changing a column from a numeric type to a string type, some databases drop the data where others will turn the numbers into their string representations.

Essentially, YMMV.

Specify attachment names

If you want to give your attachment a name, you can do this:

attachment :filename => 'my_file.txt', :body => File.read('/var/null')

It will appear to the recipient as a file named “my_file.txt” rather than something awful like “noname 1”.

Loop through matches of your regular expression-based search

If you want to loop through the matches of a regular expression, String#scan is your friend. You can do something like this:

matches = '12345'.scan(/\d/)
matches.each do |m|
  puts m
end

# => 1
# => 2
# => 3
# => 4
# => 5

Common AJAX options

See the documentation for link_to_remote to see the common AJAX options, like :before and :completed.

Looking for the docs?

Check the ClassMethods – the docs on filters are there.

The docs are in the base class

Look in ActionController::Base for the docs.

You're probably looking for the docs here

ActionController::Caching::Sweeping

The docs are in AR::Base

The docs you’re looking for are in ActiveRecord::Base

Use helpers in your ActionMailer views

It’s very easy to give your mailer access to helpers:

# Let your mailer user the ApplicationHelper methods
class MyMailer < ActionMailer::Base
  helper :application
end

Use the current URL, with changes

You can use the current URL, whatever it is, with changes, as in:

# Create a link to the current page in RSS form
url_for(:overwrite_params => {:format => :rss})

This can be super-helpful because it preserves any GET params (like search parameters)

You can't have many :through with habtm

Imagine the following

a has_many b
b has_and_belongs_to_many c
a has_many c :through => b

a.b works fine

b.c works fine

a.c throws an error!

has_many :through where the through association is a habtm is not supported in Rails. The error is:

ActiveRecord::HasManyThroughSourceAssociationMacroError: Invalid source reflection macro :has_and_belongs_to_many for has_many :stories, :through => :subcategories. Use :source to specify the source reflection

Specifying the source reflection still won’t help you though, because this kind of has_many :through isn’t supported at all.