The Difference Between Width and Flex Basis | Geddski
Within a Flexbox layout, there are multiple CSS attributes that may affect a child's basis (the initial width before flexing). You might be confused how flex-basis
, width
, min-width
and the intrinsic width of your content play together.
The attached article explains the differences. In summary:
- If a
flex-basis
is set, that is used as the basis - If no
flex-basis
is set, thewidth
is used as the basis - If neither
flex-basis
norwidth
is set, the content...
HTML forms with multiple submit buttons
Most forms have a single submit button that will save the record when pressed.
Sometimes a form needs additional submit buttons like "accept" or "reject". Such buttons usually attempt a state transition while updating the record.
To process a form with multiple buttons, your server-side code will need to know which button was pressed. To do so you can give each submit button a different [formaction]
attribute. This will override the ...
Rails routing: Using constraints to avoid "Missing template" errors
You can use constraints in your routes.rb
to avoid getting errors when wrong routes are called. Instead, the user will see a 404.
If you want multiple routes to use the same constraint you can use the block syntax:
constraints(format: 'html') do
resources :pages
resources :images
end
If you want constraints only on certain routes, you can do:
get '/users/account' => 'users#account', constraints: { format: 'html' }
Note: You can also avoid this error through [format constraints in your controllers](/makandra...
Haml Whitespace Preservation (or: Fixing Textarea Indentation in Haml)
Haml properly indents the HTML it renders. When it comes to white-space preserving content, that is a problem: the content will be rendered including the HTML indentation.
A solution is to render with tilde ~
instead of equals =
:
# bad - indented
.nest
%pre
= content
# good
.nest
%pre
~ content
In some versions of Haml + Rails, this may also be an issue for textarea
s. Fix it similarly:
# bad - indented
= form.text_area :description
# good
~ form.text_area :description
Why your Cucumber feature loses cookies when run under Selenium
When your Cucumber feature seems to forget cookies / sessions when you run it with Selenium check if the test travels in time like here:
Given the date is 2017-10-20
When I sign in
Then I should see "Welcome!"
What happens here is that the Rails application serving pages runs in 2017, but the process running your browser still lives today. This huge gap in time will expire most cookies immediately.
If all you need is to freeze the time to a date, a workaround is to travel to the future instead.
Clean code: Avoiding short versions in command options
This card is a general reminder to avoid the short version of a command option in shared code. It's much easier to understand a command and search for an option when it's written out.
You can still use the short version of the options in your own terminal or in code snippets that are more useful when they are very compact. For the latter case you often see a description of the command options one line below e.g. in posts on stackoverflow.
Example good (in code):
/usr/bin/gpg --output password.txt --decrypt password.txt.gpg
...
Git: Restore
tl;dr
git checkout
is the swiss army of git commands. If you prefer a semantically more meaningful command for restoring tasks, usegit restore
instead.With this command you can ...
- ... do unstaging -
git restore --staged
- ... discard staged changes -
git restore --staged --worktree
- ... discard unstaged changes -
git restore
- ... restore deleted files -
git restore
- ... restore historic versions -
git restore --source
- ... recreate merge conflicts -
git restore --merge
- ... specifiy...
Capybara: Working with invisible elements
When Capybara locates elements in the DOM, by default it allows only accessing visible elements -- when you are using a driver that supports it (e.g. Selenium, not the default Rack::Test
driver).
Consider the following HTML:
<div class="test1">One<div>
<div class="test2">Two</div>
With some CSS:
.test1 { display: block }
.test2 { display: none }
We will be using Capybara's find
below, but this applies to any Capybara finder methods.
Default: visible: :visible
As described above, by default Capybara finds ...
Defining and calling lambdas or procs (Ruby)
Ruby has the class Proc
which encapsulates a "block of code". There are 2 "flavors" of Procs
:
- Those with "block semantics", called
blocks
or confusingly sometimes alsoprocs
- Those with "method semantics", called
lambdas
lambdas
They behave like Ruby method definitions:
- They are strict about their arguments.
-
return
means "exit thelambda
"
How to define a lambda
-
With the
lambda
keywordtest = lambda do |arg| puts arg end
-
With the lambda literal
->
(since Ruby 1.9.1)
...
ActiveStorage: How to add a new preprocessed named version
Given there is a user with an attachable avatar:
class User < ApplicationRecord
has_one_attached :avatar
end
If you want to add a preprocessed version follow these steps:
- Add the named version and deploy
class User < ApplicationRecord
has_one_attached :avatar do |attachable|
attachable.variant :preview, resize_to_fit: [177, 177 * 9 / 16], preprocessed: true
end
end
- Preprocess this version for all existing records `bundle exec rails runner 'User.find_each { |user| user.avatar.variant(:preview).proc...
ActiveStorage: How to copy / clone an attachment from one record to another
Given there is a user with an attachable avatar:
class User < ApplicationRecord
has_one_attached :avatar
end
You can copy the avatar from one user to another user with the code below:
user_1 = User.first
user_2 = User.create!(
avatar: {
io: StringIO.new(user_1.avatar.download),
filename: user_1.avatar.blob.filename.to_s,
content_type: user_1.avatar.blob.content_type.to_s,
}
)
Note: For large attachments you might need to use a different approach to avoid memory issues.
Using Low-Level Prompts for High-Accuracy AI Coding
The key to unlocking the full potential of LLMs in coding lies in crafting precise prompts. The main challenge is learning how to structure prompts effectively to guide the model toward accurate results. Further evidence supporting this is the fact that Aider already writes ~70% of its own code (as of 02/2025). However, when starting out, your results may fall short of efficiently generating large portions of your code with the...
Git commands to discard local changes
Use case
You have uncommited changes (you can always check by using git status
), which you want to discard.
Context
Now there are several options to discard these depending on your exact situation.
The headlines will differentiate the cases whether the files are staged or unstaged.
- Staged and unstaged changes
- [Staged changes](https://makandracards.com/makandra/516559-git-commands-to-discard-local-changes#s...
RSpec: Tagging examples and example groups
In RSpec you can tag examples or example groups with any tags you like simply by saying
describe ReportCreator, slow: true do
# ..
end
describe ReportCreator do
it 'generates reports', slow: true do
# ...
end
end
You can then only run examples with these tags.
rspec --tag slow
rspec -t slow
# Using the parallel_tests gem
rake "parallel:spec[,,--tag slow]"
Or you can run all examples except the ones with a certain tag:
rspec --tag ~slow # note the ~
rspec -t ~slow
# Using the parallel_tests gem
r...
PSA: "index: true" in Rails migrations does not work as you'd expect
Several Rails migration methods accept index: true
as an option to create an index. In some cases (like #add_column
), this option is silently discarded. Know what you are doing, or use #add_index
instead.
Example
Consider the following migration.
class CreateExamples < ActiveRecord::Migration
def change
create_table :examples do |t|
t.references :category, index: true
t.boolean :positive, index: true
t.integer :number_of_participants, index: true
end
add_reference :examples, :user, index: tr...
Writing a README for a project
Rails applications and ruby gems should have a README that gives the reader a quick overview of the project. Its size will vary as projects differ in complexity, but there should always be some introductory prose for a developer to read when starting on it.
Purpose
That's already the main purpose of a project README: Give a new developer a quick overview of the project. In sketching this outline, the README should notify the reader of any peculiarity he needs to know of.
Remember that in a few months, you'll be a kind of "new ...
Google Analytics: Changing the tracked URL path
By default, Google Analytics tracks the current URL for every request. Sometimes you will want to track another URL instead, for example:
- When an application URL contains a secret (e.g. an access token)
- When you want to track multiple URLs under the same bucket
- When you want to track interactions that don't have a corresponding URL + request (e.g. a Javascript button or a PDF download)
Luckily the Analytics code snippet allows you to freely choose what path is being tracked. Simple change this:
ga('send', 'pageview');
......
The Ruby Object Model
In Ruby (almost) everything is an Object
. While this enables a lot of powerful features, this concept might be confusing for developers who have been programming in more static languages, such as Java or C#. This card should help understanding the basic concepts of Ruby's object model and how things behave.
Usage of objects in Ruby
When working with objects in Ruby, you might think of a "container" that holds metadata, variables and methods. Metadata describes stuff like the object's class or its object_id
whi...
Installing Python packages using pip on Ubuntu 24.04
Ubuntu 24 added some guarding for Python packages which no longer allows installing applications through pip on system level. Instead, you are presented with this error message:
error: externally-managed-environment
× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
python3-xyz, where xyz is the package you are trying to
install.
If you wish to install a non-Debian-packaged Python package,
create a virtual environment using python3 -m venv path/to/venv.
Then use...
Shell script to magically configure display setup
Here is a bash script that I use to auto-configure displays on Ubuntu 24.04 with Xorg.
Background
- Ubuntu always sets the primary display to the 1st (i.e. internal) display whenever I connect to a new Dock/Hub.
- I want my primary display to be the large display.
- My notebook is always placed left of external displays, so the 2nd display will be the center (or only) external display and should be primary.
- I also want all my displays to be placed horizontally, but bottom-aligned (the default would be aligned at their top edges)....
Debug your Postgres SQL query plan
When debugging slow SQL queries, it’s helpful to understand the database engine's query plan. Whenever you execute a declarative SQL query, the database generates a "query plan" that outlines the exact steps the engine will take to execute the query. Most of the time, we don’t need to worry about this plan because SQL engines are highly optimized and can generate efficient execution strategies automatically. However, if a query is slow, inspecting the generated plan can help identify bottlenecks and optimization opportunities.
If you're usi...
Rails and Postgres: How to test if your index is used as expected
This is a small example on how you can check if your Postgres index can be used by a specific query in you Rails application. For more complex execution plans it might still be a good idea to use the same path of proof.
1. Identify the query your application produces
query = User.order(:last_name, :created_at).to_sql
puts query
# => SELECT "users".* FROM "users" ORDER BY "users"."last_name" ASC, "users"."created_at" ASC
2. Add an index in your migration and migrate
add_index :users, [:last_name, :created_at]...