TIL

ActiveRecord provides default_scope, which you can use to control how records are returned. An example: # app/model/chapter.rb class Chapter < ActiveRecord::Base default_scope { order(:title) } end Now, instead of this (ordered by ID): Chapter.all.pluck(:title).take(5) => ["BALINESE CAUSE", "BUILDING RAT", "TAIL", "LILAC MERCURY", "PUMP SQUARE"] We get this: Chapter.all.pluck(:title).take(5) => ["AFGHANISTAN COAT", "ALCOHOL GONG", "ANTARCTICA BULL", "ASPARAGUS", "BALINESE CAUSE"] Beware, this decision can lead to inexplicable behavior down the road. Use with caution. One use case I’ve heard is soft deletes. We might not want soft-deleted records appearing in .all: ...

Vim has excellent commands for changing the contents of parentheses (ci(), brackets (ci[), and squiggly braces (ci{) (as well as single quotes, double quotes, backticks, etc.). But what about tags? Place your cursor anywhere inside the tags, type cit in Visual mode, and this: <div>Begone</div> Becomes: <div></div> d works too, but I prefer c because it puts you in Insert mode at the end of the opening tag, ready to type. ...

Haml’s design makes HTML and Ruby tricky to mix inline. But we have Haml helper methods to make it easier. Here is succeed in action: Developer at = succeed ', ' do = link_to "Hashrocket", "https://hashrocket.com/" This becomes: Developer at <a href="https://hashrocket.com/">Hashrocket</a>, Notice the comma at the end, outside of the a tag? precede and surround work in a similar fashion, and do what we’d expect. http://haml.info/docs/yardoc/file.REFERENCE.html#succeed

Vim has commands built-in to increment and decrement numbers: CTRL-A and CTRL-X, respectively. Combining this with a macro was a technique we tried today to build a large database migration. We ended up finding a more efficient solution, but it’s still a very magical key combination. Check out :help CTRL-A for more info. h/t Josh Branchaud

We had a testing issue this week when a button’s text save changes! was rendering as SAVE CHANGES!, due to the CSS property text-transform: uppercase. How do you test that? One technique is to use RSpec’s match method, and include case insensitivity with i (explored earlier here): > button_text = "foo" => "foo" > expect(button_text).to match("FOO") RSpec::Expectations::ExpectationNotMetError: expected "foo" to match "FOO" # stuff > expect(button_text).to match(/FOO/i) => true We ultimately hard coded the expectation to match("FOO"), because allowing fOo and FoO seemed too permissive. But it remains an option.

Today I found a way to assert that an edit form’s inputs include a record’s saved data. I think it strikes a good balance between broad and narrow scope. # spec/features/user_edits_kit_spec.rb within 'form' do expect(page).to have_selector("input[value='Default copy.']") end This asserts that some content is inside an input field in the form, rather than just anywhere on the page. You can narrow the scope as needed.

Today I was cleaning up a test with an extra empty line at the top of the file, away from my Vim cursor. I wanted to delete it… without moving the cursor. It seems like Vim almost lets you do this, with :[range]d. But it leaves the cursor on the deleted line, which isn’t very magical. This is the hack we found: :[range]d Then: '' '' returns the cursor to the last jump point. ...

Today I used Ruby’s Kernel::abort for the first time. It’s one of those incredibly useful methods I can’t believe I’ve never seen before. Observe: # abort.rb {1} def no_message abort end def message abort('Process terminated') end $ irb 2.2.2 :001 > require './abort' => true 2.2.2 :002 > no_message $ irb {1} 2.2.2 :001 > require './abort' => true 2.2.2 :002 > message Process terminated $ Use it to bail from a script. ...

Today I learned that I have thirty-nine Postgres databases on my computer, after running this command inside psql: \l ; Each one is small, but I don’t like to carrying around old data. I ended up dropping nine of them, with: drop database foo_development; For a lighter storage and cognitive load.

This week I learned that attr_reader is more performant than a simple getter method. Here’s a gist from five years ago where Aaron Patterson explains: https://gist.github.com/pjb3/629716 I ran that same benchmarking script today on Ruby 2.2.3. The gap has narrowed, but still exists: ruby-2.2.3 Rehearsal ----------------------------------------------- method 0.070000 0.000000 0.070000 ( 0.074840) attr_reader 0.050000 0.000000 0.050000 ( 0.052603) -------------------------------------- total: 0.120000sec user system total real method 0.070000 0.000000 0.070000 ( 0.072229) attr_reader 0.050000 0.000000 0.050000 ( 0.053374) I like attr_reader because it’s a Ruby convention and is one line instead of three. Now, I also like its performance relative to a getter. ...