TIL

Today while writing a Vim regex to change every instance of it (ignoring larger matches like itemized), we stumbled upon Vim regex word boundary matching. Given this file: foo foobar The following Vim regex will match on both the first and second line: :%s/foo/baz/g But with word boundaries, we’ll only match (and change) the first line, because only the first foo is a standalone word: :%s/\<foo\>/baz/g

Tagging releases with Git is a good idea. In case your tags get off track, here is how you delete a Git tag locally and on a remote: $ git tag -d abc $ git push origin :refs/tags/abc To git@github.com:hashrocket/hr-til - [deleted] abc It gets trickier if you’re using Semantic Versioning, which includes dots in the tag name. The above won’t work for v16.0.0. This will: $ git tag -d v16.0.0 $ git push origin :v16.0.0 To git@github.com:hashrocket/hr-til - [deleted] v16.0.0

In my never-ending quest to better summarize my work at the end of the day using computers, I discovered today the Git --author flag. It works like this: $ glg --since=midnight --author=dev+jwworth+mikechau@hashrocket.com * 4ba91a8 (HEAD, origin/checkout, checkout) Add guard for manual entry of employee discount * 3a4e4c9 Seed a coupon and code and auto-apply in preview * cb1adee Add discount ... The alias glg is discussed here. I use this when multiple developers or teams are committing throughout the day to the same repository, to disambiguate our work from others. Ready to paste into your billing software of choice.

Today I learned a great way to count the links in a README or link collection. Vim Regex! :%s/- \[//n In Vimspeak: On every line, find all of the times where - [ (the beginning of a Markdown bulleted hyperlink) occurs, count them, and report the number of matches. See :help substitute in Vim for more information. h/t Josh Branchaud

Today I learned how to query the size of a Postgres array. There are (at least) two methods that work. The first is array_length. This requires you to know the array dimension you seek; a useful filter, although most of the time this will probably be 1: hr-til_development=# select title from posts hr-til_development=# where array_length(slack_notified_at_likes_threshold, 1) = 1; title ------------------------------------------- Because Javascript Percent Notation DIY Grids for Designing UI in Illustrator (3 rows) When the dimension is 1, a more terse solution is cardinality: ...

Today I added an array of integers to a Postgres table, and like all such migrations, it will default to null for each new record. This was a problem, because I wanted to use Rails 4’s built-in Postgres array support to make decisions based on that data. Ruby array methods like include? will raise NoMethodError: undefined method 'include?' for nil:NilClass if that array is ever nil, which it is by default. ...

This afternoon my pair and I spent quite a while on a subtle bug. The culprit? Variable hoisting. Take this file: class Test def self.hoist require 'pry'; binding.pry; bar = 1 end end Test.hoist When we hit the PRY debugger, what will the value of bar be? I would have thought it would raise NameError, because bar has seemingly not yet been defined. Wrong: $ ruby test.rb From: /test.rb @ line 4 Test.hoist: 2: def self.hoist 3: require 'pry'; binding.pry; => 4: bar = 1 5: end [1] pry(Test)> bar => nil When Ruby parses a file, it ‘hoists’ each variable to the top of its scope, declaring and setting it to nil, even if that variable is never assigned by our code. So variables inside an if false conditional get hoisted and set to nil, as described in this blog post. ...

Today I found a great command in Pathogen.vim, :Helptags. This is a riff off :helptags {dir}, a Vim feature that builds helptags for directory {dir}. :Helptags does the same for all the directories in your runtimepath, which defaults on Unix and Mac OS X to: "$HOME/.vim, $VIM/vimfiles, $VIMRUNTIME, $VIM/vimfiles/after, $HOME/.vim/after" The use case here is when you’ve just loaded a new plugin into your Vim bundle, you open up Vim, and :h {my_new_plugin} isn’t ‘helping’ you out.

Have you ever wondered about those secret keys found in config/secrets.yml of your Rails app? The comments generated in that file describe the keys as ‘used for verifying the integrity of signed cookies.’ Great… but what if they become compromised? Or we need to change them? We can generate new ones. Rails provides rake secret for just this purpose. The source code is here. It’s pretty simple; the code simply requires SecureRandom and spits out a string. If you want to be really clever, you can pipe the string directly into your Vim buffer for the config file, with :.! rake secret. ...

This week Josh Branchaud wrote about show-models in Pry-rails: http://til.hashrocket.com/posts/62f61ee06f-show-rails-models-with-pry This method has two nice variants. show-model User shows you that model, useful in a large database. show-models also accepts --grep for searching: [1] pry(main)> show-models --grep published Post id: integer title: string published_at: datetime # 'published' is highlighted