Sometimes I want to install some apps, but the site is blocked by GFW. I only have a Shadowsocks server, so I made some research how to setup up an HTTP and HTTPS proxy using Shadowsocks server.

The solution is using Shadowsocks client, which will establish a socket proxy, then convert the socket proxy to HTTP/HTTPS proxy using polipo.

Ansible uses YAML to define tasks, playbooks and handlers. If the files follow some conventions, it is easy to index them using Exuberant Ctags.

It is a headache to find an available keyboard shortcuts in Mac OS X. I used Option + Letter and Shift + Option + Letter before, since they are preserved for inputting special characters. It has some problems:

  • Emacs and terminal require a modifier for Meta. I choosed Command. It means if I want to use application shortcut with Command in these applications, such as Command+Q to quit the application, I have to use the right one.
  • I always forget the shortcuts. Although I have listed them in a sheet, it is a pain to keep it synchronized with the shortcuts defined every where.

I switched to a new solution using keystroke sequence shortcuts recently. All my global shortcuts start with Command+M (⌘M). A menu is displayed when I typed prefix. If I forget the shortcut, I just need to glance through the menu.

Auto Toggle MacBook Internal Keyboard

I prefer using external keyboard with my MacBook. When no external monitors are used, a typical setup is placing the keyboard above the internal one, so I can still use the internal touchpad.

But sometimes the external keyboard may press some keys of the internal keyboard. There is a solution to disable the internal keyboard, but it is tedious to run the command manually.

# Disable, ignore the warning
sudo kextunload /System/Library/Extensions/AppleUSBTopCase.kext/Contents/PlugIns/AppleUSBTCKeyboard.kext/
# Enable
sudo kextload /System/Library/Extensions/AppleUSBTopCase.kext/Contents/PlugIns/AppleUSBTCKeyboard.kext/

Fortunately, Keyboard Maestro supports executing scripts when a USB device is attached or detached.

ActiveRecord has two query methods to eager load associations, includes and preload. Although the documentation of preload says

Allows preloading of args, in the same way that includes does.

Indeed the two methods have some differences.

In simple words, prefer includes to eager load associations. Use preload only when

  • you want to customize select columns, or
  • you meet error “Can not eagerly load the polymorphic association”.

ActiveRecord has two methods to remove duplicates. Method uniq and option distinct: true in method count. I thought uniq.count and count(distinct: true) were identical. Indeed, uniq.count still counts duplicates, and count(distinct: true) must be used here.

In simple words, use uniq to get unique result set, use count(distinct: true) to count unique result.

SVG can use percentage as unit, but it is often more convenient to use px as unit. Framework such as d3 also uses px internally. However, it is still easy to scale an SVG using attributes viewBox and preserveAspectRatio even px is used as unit internally.

This is original posted on intridea blog.

I recently worked in a Rails project with Peter (@sporkd). The project is intended to be used as a sub-site, and should be served under sub-URI. After google, we ended up by setting config.assets.prefix and wrapped all routes in scope. The solution is simple and worked well. But soon, some weird bugs were found, and Peter was successfully isolated the problem to session (see demo sporkd/asset_prefix_test)

After several hours debugging, I finally found out the cause. To make a long story short, the routes configured in routes.rb should not start with config.assets.prefix, otherwise session save is skipped. The demo sporkd/asset_prefix_test can be fixed by simply setting config.assets.prefix to /one/assets. You also get a bonus by setting a unique prefix for assets, since it is easy to add expiration header for assets in web server.

# ^Xa to insert all matches
zle -C all-matches complete-word _generic
bindkey '^Xa' all-matches
zstyle ':completion:all-matches:*' old-matches only
zstyle ':completion:all-matches::::' completer _all_matches

UPDATE: The snippet above brings insert-completions to zsh. Thanks, Trevor Joynson, who has provided the solution in comment.

Command insert-completions (see man bash) is the feature I most miss in bash.

[insert-completions] Insert all completions of the text before point that would have been generated by possible-completions.

Its default binding is M-*, a.k.a, Alt-Shift-8 or Meta-Shift-8.

It is useful for simple batch operations, such as removing all git branches starting with feature/.

After I switched to zsh, I have been looking for a similar command, but for no results. However, I just discovered the zsh way to select multiple completions recently, using accept-and-hold (see man zshzle).

[accept-and-hold] Push the contents of the buffer on the buffer stack and execute it.

The default binding is M-a (a.k.a, Alt-a or Meta-a). If the command line has input content ls, M-a executes the line ls without clearing the input.

It seems unrelated. But if completion menu is activated and a menu item is selected (the simplest way is Tab twice), accept-and-hold accepts the current menu item without closing completing menu. So it is possible to select multiple items by navigating to wanted items, and type M-a to select them.

Jasmine is a behavior-driven development framework for testing JavaScript code. It does not depend on any other JavaScript frameworks. It does not require a DOM. And it has a clean, obvious syntax so that you can easily write tests.

It is very easy to integrate Jasmine into Rails, since the team provides the jasmine gem. The jasmine gem also supports assets pipeline, just prepend assets/ to file path. For example, app/assets/javascripts/ can be referred as assets/application.js in jasmine.yml src_files.

However, spec_files does not support assets pipeline, so the files in spec/javascripts cannot be written in CoffeeScript. But if spec/javascripts is appended to assets pipeline paths, the spec files can be added to src_files in jasmine.yml.

This post explains how to apply such trick, and how to integrate jasmine gem with guard-jasmine and travis.

I also created a demo repository, see its commits for integration steps.