Notes posted by mutru

Testing Net:HTTP connections

You can use this excellent library to stub Net:HTTP connections in your automatic tests:

http://github.com/bblimke/webmock

Receiving data over UDP

It’s perfectly normal to receive ‘X’ strings with Ruby’s UDP sockets before the actual content.

Consider the following example:

require 'socket'

PORT = 5500

socket = UDPSocket.new
socket.bind('', PORT)

for i in 1..10
  IO.select([socket])
  p socket.recvfrom_nonblock(4096)
end

Now, sending data with netcat:

echo "Hello APIdock" | nc -vv -u 127.0.0.1 5500

The application would output:

["X", ["AF_INET", 61755, "localhost", "127.0.0.1"]]
["X", ["AF_INET", 61755, "localhost", "127.0.0.1"]]
["X", ["AF_INET", 61755, "localhost", "127.0.0.1"]]
["X", ["AF_INET", 61755, "localhost", "127.0.0.1"]]
["Hello APIdock\n", ["AF_INET", 61755, "localhost", "127.0.0.1"]]

Streaming XML with Builder

To generate larger XMLs, it’s a good idea to a) stream the XML and b) use Active Record batch finders.

Here’s one way of doing it:

def my_action
  @items = Enumerable::Enumerator.new(
    Item.some_named_scope,
    :find_each,
    :batch_size => 500)

  respond_to do |format|
    format.xml do
      render :text => lambda { |response, output|
        extend ApplicationHelper

        xml = Builder::XmlMarkup.new(
          :target => StreamingOutputWrapper.new(output),
          :indent => 2)
        eval(default_template.source, binding, default_template.path)
      }
    end
  end
end

The Builder template does not need to be modified.

Shared examples

Use it together with share_examples_for like this:

share_examples_for "a shape" do
  it "should have a color" do
    # ...
  end

  it "should have a center point" do
    # ...
  end
end

describe "a circle" do
  it_should_behave_like "a shape"

  it "should be round" do
    # ...
  end
end

Typical stub! usage

Typically you would call

my_object.stub!(:updated_at).and_return(time_object)

Test if one array includes the elements of another v2

Maybe a bit more readable way to write the previous snippet would’ve been

puts "yay" if [1, 2, 3].all? { |i| (1..9).include?(i) }
# => "yay"

puts "nope" if [1, 2, 3, 'A'].any? { |i| not (1..9).include?(i) }
# => "nope"

Usage examples

Basic usage:

User.should_receive(:find).with(:all, anything).and_return("hello world")

Now:

User.find(:all, :conditions => "foo")  #=> "hello world"

But you can also use blocks for more complex matching logic. For example:

User.should_receive(:find) { |*args|
  if args.size == 2
    "received two arguments"
  else
    "something else"
  end
}.at_least(:once)

Now:

User.find(:all, :conditions => "bar")  #=> "received two arguments"
User.find(5)                           #=> "something else"

Of course normally you’d return mocks instead of strings.

Multiline regexps

A shortcut for multiline regular expressions is

/First line.*Other line/m

(notice the trailing /m)

For example:

text = <<-END
  Hello world!
  This is a test.
END

text.match(/world.*test/m).nil?  #=> false
text.match(/world.*test/).nil?   #=> true

Implemented in database adapters

These methods are not implemented in the abstract classes. Instead, all database adapters implement these separately, if the feature is supported.

Convert strings to Dates

Uses the undocumented Date._parse method. Some usage examples:

'06/15/2008'.to_date         # => Sun, 15 Jun 2008
'20080615'.to_date           # => Sun, 15 Jun 2008
'2008-06-15'.to_date         # => Sun, 15 Jun 2008
'Sun, 15 Jun 2008'.to_date   # => Sun, 15 Jun 2008

Using counters with collections

When you’re rendering a collection partial, the partial_name_counter variable contains the position of the current element in the collection. For example:

<%= render(:partial => 'example', :collection => %w(rails-doc is cool)) %>

Now in _example.html.erb:

<p>Element: <%= example %> (index: <%= example_counter %>)</p>

It would produce:

<p>Element: rails-doc (index: 1)</p>
<p>Element: is (index: 2)</p>
<p>Element: cool (index: 3)</p>

As you can see, indexing starts from 1.

around_filter code example

This is how it’s used:

around_filter do |controller, action|
  do_your(:stuff) do
    action.call
  end
end

Rails 2.1 caching internals

Rails 2.1 caching features are pretty much undocumented. Rob Anderton has documented some internal stuff here:

http://www.thewebfellas.com/blog/2008/6/9/rails-2-1-now-with-better-integrated-caching

Using memcached as a session store

Because of Ruby’s CGI library limitations, store cannot have any configuration options. Basically this means that you cannot easily run memcached on a different port (or with any non-default settings for that matter).

You can bypass this limitation with this ugly hack (environment.rb):

cache_params = *([memcache_servers, memcache_options].flatten)
CACHE = MemCache.new(*cache_params)
ActionController::CgiRequest::DEFAULT_SESSION_OPTIONS.merge!({ 'cache' => CACHE })

In your initializer block, just configure session_store normally:

config.session_store = :mem_cache_store

I think this should be fixed to work like cache_store= does.