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Douglas Teoh dteoh

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dteoh / arel_select_star_from_table.rb
Last active Dec 2, 2019
Select all columns of an Arel table
View arel_select_star_from_table.rb
users = User.arel_table
query = users.project(users[])
dteoh /
Last active Feb 1, 2017
Checksumming backups

par2 is not just for checksumming and recovering Usenet binaries, you can use it for your backups as well.

In my case, I wanted to make sure my RAW and JPG files don't get corrupted by bitrot.

Generating the checksum:

$ cd /the/directory/where/files/are/kept
$ par2 c something.par2 *
$ shasum -a 256 * > shasum256.txt
dteoh / hash_to_numeric.rb
Last active Mar 22, 2016
Get numeric value from hash digest
View hash_to_numeric.rb
require 'digest'
key = 'the value to hash'
num = Digest::MD5.digest(key).unpack('L').first
dteoh /
Created Jul 12, 2016
PUT or POST JSON in a Rails 5 ActionDispatch::IntegrationTest

In Rails 5, the preferred base class for testing controllers is ActionDispatch::IntegrationTest.

If you have an API that receives parameters as JSON request bodies, here are some helper methods to facilitate testing:

class ActionDispatch::IntegrationTest
  def put_json(path, obj)
    put path, params: obj.to_json, headers: { 'CONTENT_TYPE' => 'application/json' }
dteoh /
Last active Apr 28, 2018
Adding extra test paths to Rails 5 `rails test` command

In Rails 4.x, you could add extra test paths to rake test by overriding the Rake task like so:


namespace :test do do |t|
    paths = ['test/**/*_test.rb']
    paths << 'engines/foo_engine/test/**/*_test.rb'
dteoh /
Created Feb 23, 2017
Preventing macOS from sleeping

There is a built-in command line utility caffeinate that can be used to prevent macOS from sleeping.

To prevent macOS from sleeping before a process with given PID exits:

$ caffeinate -w PID

To prevent macOS from sleeping for the next N seconds:

dteoh / puma_rb_backtrace.txt
Created Apr 10, 2017
Puma rb_backtrace() crash in lldb
View puma_rb_backtrace.txt
(lldb) expression (void) rb_backtrace()
/Users/dteoh/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/puma-3.8.2/lib/puma/plugin/tmp_restart.rb:22: [BUG] pthread_cond_wait: Invalid argument (EINVAL)
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin16]
-- Crash Report log information --------------------------------------------
See Crash Report log file under the one of following:
* ~/Library/Logs/CrashReporter
* /Library/Logs/CrashReporter
* ~/Library/Logs/DiagnosticReports
* /Library/Logs/DiagnosticReports
dteoh / .gitconfig
Created Mar 17, 2019
Use Neovim as git mergetool
View .gitconfig
tool = vimdiff
keepBackup = false
[mergetool "vimdiff"]
cmd = nvim -d $LOCAL $REMOTE $MERGED -c '$wincmd w' -c 'wincmd J'
dteoh /
Last active Apr 2, 2019
A pattern for encoding records with bs-json

A pattern for encoding records with bs-json

If you have a record type like:

type post = {
  title: string,
  body: string,
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