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.

HHKB Above MacBook Keyboard
HHKB Above MacBook Keyboard

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.


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/application.js.coffee 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.


When I implement time input feature for 19wu (an open source ticket sale system), I want to split the datetime into date and time parts, so JavaScript date picker and time picker can be used. This post introduces two methods I found.

compound datetime input
Compound datetime input

composed_of utilizes assign_multiparameter_attributes trick like datetime_select, and fields_for mocks an association.

The github repository doitian/rails-compound-input-demo contains demos for both methods.


There are two TAB's in Emacs, (kbd "TAB") (\t, [9]) and (kbd "<tab>") ([tab]). If modes like yasnippet and auto-complete want to bind on TAB, their trigger key must be the same with the original Tab command. Since Emacs binds indent-for-tab-command on (kbd "TAB"), so it's better to use it as the trigger key. Yasnippet binds to it by default, It is also easy to setup auto-complete to trigger using Tab.

;; trigger using TAB and disable auto start
(custom-set-variables
 '(ac-trigger-key "TAB")
 '(ac-auto-start nil)
 '(ac-use-menu-map t))

But in some modes (ruby-mode, markdown-mode, org-mode), the command is bind to (kbd "<tab>"), when the real Tab key is typed, the function bind on (kbd "<tab>) has higher priority, so yasnippet and auto-complete are not invoked. It is easy to fix by moving the keybinding:

(defun iy-tab-noconflict ()
  (let ((command (key-binding [tab]))) ; remember command
    (local-unset-key [tab]) ; unset from (kbd "<tab>")
    (local-set-key (kbd "TAB") command))) ; bind to (kbd "TAB")
(add-hook 'ruby-mode-hook 'iy-ac-tab-noconflict)
(add-hook 'markdown-mode-hook 'iy-ac-tab-noconflict)
(add-hook 'org-mode-hook 'iy-ac-tab-noconflict)

Yasnippet tries functions in yas/prompt-functions when it needs user to select one choice, such as selecting snippets with the same trigger key, such as helper method yas/choose-value.

popup is a visual popup interface library extracted from auto-complete by its author. It has better look and feel than all the built-in yas/prompt-functions. Also it is easy to customize, and its isearch mode is very efficient, the items are filtered on-the-fly when typing.

choises
Choises
filter by keyword
Popup isearch by typing "f"

The integration is easy. Load popup.el, implement one prompt function and add it to yas/prompt-functions.

(require 'popup)
(require 'yasnippet)

;; add some shotcuts in popup menu mode
(define-key popup-menu-keymap (kbd "M-n") 'popup-next)
(define-key popup-menu-keymap (kbd "TAB") 'popup-next)
(define-key popup-menu-keymap (kbd "<tab>") 'popup-next)
(define-key popup-menu-keymap (kbd "<backtab>") 'popup-previous)
(define-key popup-menu-keymap (kbd "M-p") 'popup-previous)

(defun yas/popup-isearch-prompt (prompt choices &optional display-fn)
  (when (featurep 'popup)
    (popup-menu*
     (mapcar
      (lambda (choice)
        (popup-make-item
         (or (and display-fn (funcall display-fn choice))
             choice)
         :value choice))
      choices)
     :prompt prompt
     ;; start isearch mode immediately
     :isearch t
     )))

(setq yas/prompt-functions '(yas/popup-isearch-prompt yas/no-prompt))