paul.annesley.cc

MethodHuntingDelegator

2012-01-09T17:51:00+11:00

I was implementing search in a Ruby app where the results objects were instances of a mix of model classes. Each one had what could be considered a title and a description, but the method names were inconsistent.

Wrapping each result in a SearchResult decorator to normalize the interface seemed like a good idea. Ruby provides an abstract Delegator and a concrete SimpleDelegator which gets most of the way there.

To normalize the method interface, I wrote an extension of SimpleDelegator with a #hunt_and_call(*candidates) method, which finds and calls the first method of the candidate list which the delegate responds to.

Here’s the example calling code:

class Book < SomeModelThing attr_reader :title, :blurb end class Course < SomeModelThing attr_reader :name, :description end class SearchResult < MethodHuntingDelegator def description hunt_and_call :description, :blurb end def title hunt_and_call :title, :name end end # simulate the results of a search with mixed result types results = [ Book.first, Course.first ].map(&SearchResult.method(:new)) results.each { |r| puts "#{r.title}: #{r.description}" }

And the MethodHuntingDelegator implementation:

require "delegate" class MethodHuntingDelegator < SimpleDelegator def hunt_and_call *candidates hunt_method(*candidates).call end private def hunt_method *candidates __getobj__.method candidates.detect( ->{ raise Error.new(candidates, __getobj__) }, &__getobj__.method(:respond_to?) ) end class Error < StandardError def initialize candidates, object super "#{candidates.inspect} not implemented by #{object.inspect}" end end end

And of course:

require "spec_helper" require "method_hunting_delegator" describe MethodHuntingDelegator do context "decorating a string" do let(:delegate) { "abcd" } let(:delegator) { MethodHuntingDelegator.new(delegate) } describe "#hunt_and_call" do it "delegates [ :not_a_method, :length, :upcase ] to String#length" do delegator.hunt_and_call(:not_a_method, :length, :upcase).should == 4 end it "raises MethodHuntingDelegator::Error for [ :nope_A, :nope_B ]" do expect do delegator.hunt_and_call(:nope_A, :nope_B) end.to raise_error(MethodHuntingDelegator::Error) end end end end

Completely insane? Useful enough for a gem? Better way of going about it? Give me hell in the gist comments.

Camera Buyers Guide — The Verge

2012-01-09T10:50:00+11:00

Ridiculously good article on digital cameras at The Verge, worth reading even if you’re not in the market for one.

What we’re seeking to do here is help you make an informed decision by separating the meaningful data from the meaningless. This is a guide to discerning the things that will make a recognizable difference in your photographic experience and results. We’ve selected a few of our favorite cameras in the categories below, but those will change over time, whereas the rest of this advice will (hopefully) remain relevant for a long time to come.

Why can’t there be more content of this quality on the Internet?

Todokyo

2011-02-11T11:24:53+11:00

Interesting looking todo client-side web app..

It works like you’d expect, with a couple restrictions: First, every morning it starts over fresh. Your list from the day before is thrown in the trash. This, hopefully, will encourage the completion of all tasks each day and discourage the addition of frivolous items. Second, there’s no reordering. I want to trust my subconscious; if I add a task before another, then it’s because my mind has determined it’s priority by remembering it sooner.

via @toolmantim

Email with Amazon SES and Rails 3

2011-02-06T19:48:31+11:00

The always excellent GIANT ROBOTS describes using Amazon’s new Simple Email Service for sending mail from Rails 3, using the aws-ses gem.

An intro to modern OpenGL

2010-05-12T21:29:00+10:00

An excellent OpenGL tutorial; beware other documentation and tutorials which endorse deprecated APIs and practices.

Modern enough to be applicable to OpenGL ES 2.0 (and therefore WebGL), which requires vertex and fragment shaders to be written in OpenGL Shader Language to take advantage of the programmable rendering pipeline, and which removes much of the procedural (glBegin/glEnd) API.

Adapting this tutorial to Cocoa Touch for iPhone/iPad OpenGL ES 2.0 development was relatively easy, and beat any iPhone OS specific documentation for ES 2.0 that I’ve found.

git-ff for git 1.7+

2010-05-12T20:07:00+10:00

Provides ‘git ff’ to quickly fast-forward your current branch to the tracked remote when possible.

It’s ‘git pull –ff-only’ for those who do their own fetching, and besides, ‘git ff’ is quicker :)

Drop it in your path somewhere; depends on Git 1.7+ for the new –ff-only parameter.

mustache: logic-less templates

2010-03-30T21:18:00+11:00

Nice simple template format, implementations in Ruby, Python, JavaScript, PHP and more. Similar to Django templates in simplicity, syntax and sensible constraint of logic.

toto

2010-02-10T00:46:19+11:00

Tiny blog engine in Ruby and Rack, uses flat git-managed content files containing YAML & ERB/Markdown, handles comments via disqus, leaves caching to HTTP.

Machinarium

2010-01-22T14:03:56+11:00

A puzzle point-and-click adventure game with a nice ambient soundtrack and a Oddworld: Abe’s Oddysee feel about it. Implemented in flash, free demo.

Semantic Versioning

2009-12-16T14:13:37+11:00

Simple version number specification for systems which expose a public API. The format is major.minor.patch (e.g. 3.0.12); major indicates backwards incompatible, minor indicates backwards compatible, and 0.x.x indicates rapid development.

The Go Programming Language

2009-11-11T16:05:50+11:00

New programming language from Google: performance like C, dynamic like Python, concurrent like Erlang.

node.js

2009-11-10T10:18:13+11:00

Event driven network IO for V8 JavaScript.

v8 JavaScript Engine

2009-11-10T10:17:01+11:00

Google’s JavaScript engine as seen in Chrome, runs standalone or embedded in C++

jaml - GitHub

2009-11-09T09:04:33+11:00

Jaml tries to emulate Ruby’s Haml library, making it easy to generate HTML in your JavaScript projects.

Conflict free DNS and routes with multiple DHCP interfaces

2009-10-27T11:57:00+11:00

The Problem

Running DHCP on two or more network interfaces inevitably leads to conflicting or unpredictable DNS and default route settings.

For development at home and work, I use an Ubuntu virtual machine running on Mac OS. To ensure I have a predictable IP address regardless of what network I’m on, the VM primary network interface is NATed, so it gets an IP address from VMware’s DHCP server. To let my co-workers access HTTP on my virtual machine, I have a second network interface which is bridged

The biggest symptom of the problem is complete loss of connectivity when I switch between home and office, and the default route from the previous location is retained.

The Solution That Should Work

DHCP client configuration lets you specify which details you want to request from the DHCP server.

The request statement

request [ option ] [, … option ];

The request statement causes the client to request that any server responding to the client send the client its values for the specified options. Only the option names should be specified in the request statement - not option parameters. By default, the DHCP server requests the subnet-mask, broadcast-address, time-offset, routers, domain-name, domain-name-servers, host-name, nis-domain, nis-servers, and ntp-servers options.

So it should be possible to omit ‘routers’ and ‘domain-name-servers’ from the ‘request’ statement of the bridged interface, and all should be good. However, it seems that some DHCP servers (like in my Linksys router at home) send a ‘router’ anyway, and the DHCP client respects it despite not having requested it.

The Solution That Does Work

The solution that seems to work reliably is to write a simple dhclient-enter-hook to unset any unwanted details before they are processed.


# /etc/dhcp3/dhclient-enter-hooks.d/bridged-eth1

if [ "$interface" = eth1 -a -n "$new_routers" ]; then
        echo Discarding eth1 routers: $new_routers
        unset new_routers
fi
if [ "$interface" = eth1 -a -n "$new_domain_name_servers" ]; then
        echo Discarding eth1 dns servers: $new_domain_name_servers
        unset new_domain_name_servers
fi

proxymachine - GitHub

2009-10-22T11:46:43+11:00

Awesome looking Ruby/EventMachine TCP proxy from GitHub that does content-based routing to a backend. Opens a proxy to a backend once the read buffer contains enough information for a ruby block to return the desired backend address.

sstrudeau’s jquery-dropper at master - GitHub

2009-10-15T18:27:01+11:00

jQuery plugin, uses Canvas to provide an “eye dropper” color picker for same-domain images based on their pixel data.

Cloudvox - API-driven phone calls

2009-10-12T21:37:01+11:00

Make and receive calls with JSON over RESTful HTTP, with flexible pricing.

Unicorn! - GitHub

2009-10-12T17:19:32+11:00

GitHub on their switch from nginx->haproxy->mongrel to nginx->unicorn stack, and why the Unicorn model rocks.

gRaphaÃ«l â Charting JavaScript Library

2009-10-08T10:48:56+11:00

Graph and chart plugin for Raphaël, by Dmitry Baranovskiy.