...do not use request.xhr? to decide that. Use respond_to. I've too often seen code like this: def show # ... if request.xhr? render json: @user.as_json else # renders default HTML...
...just plain wrong. Web browsers often fetch JSON via XHR, but they (should) also send the correct Accept HTTP header to tell the server the data they expect to receive...
...Object into Integer (TypeError) Integer(2) # 2 Integer("11", 2) # 3 This is very similar but not identical to to_i: "2".to_i # 2 "foo".to_i # 0
...an instance of Object (NoMethodError) 2.to_i # 2 "11".to_i(2) # 3 Integer() supports a exception: false variant, which is very handy to cast user input without any exception...
...table, two things happen: Rails tries to load all involved records in a huge single query spanning multiple database tables. The preloaded association list is filtered by the where condition...
...you only wanted to use the where condition to filter the containing model. The second case's behavior is mostly unexpected, because pre-loaded associations usually don't care about...
This is somewhat similar to the touch command of Linux: FileUtils.touch 'example.txt', :mtime => Time.now - 2.hours If you omit the :mtime the modification timestamp will be set to the current time...
The nokogiri gem provides different packages for several platforms. Each platform-specific variant ships pre-built binaries of libxml2, e.g. x86_64-linux includes binaries for 64bit Linux on Intel/AMD...
...This significantly speeds up installation of the gem, as Nokogiri no longer needs to compile libxml2. However, this also means that for each security issue with libxml2, Nokogiri maintainers have...
...is a cron replacement. It runs as a lightweight, long-running Ruby process which sits alongside your web processes (Mongrel/Thin) and your worker processes (DJ/Resque/Minion/Stalker) to schedule recurring work at...
...particular times or dates. For example, refreshing feeds on an hourly basis, or send reminder emails on a nightly basis, or generating invoices once a month on the 1st...
Download buttons can be difficult to test, especially with Selenium. Depending on browser, user settings and response headers, one of three things can happen: The browser shows a "Save as...
...dialog. Since it is a modal dialog, we can no longer communicate with the browser through Selenium. The browser automatically downloads the file without prompting the user. For the test...
Running rails server will start a local server that you can access via http://localhost:3000. When you are working on multiple web apps, they will likely set cookies with...
...generic names on localhost. This is annoying, since you will sign out your current user whenever you switch to another app. A better way is to use our own daho.im...
cpulimit is a simple program which attempts to limit the cpu usage of a process (expressed in percentage, not in cpu time). This is useful to control batch jobs, when...
...eat too much cpu. It does not act on the nice value or other scheduling priority stuff, but on the real cpu usage. Also, it is able to adapt itself...
...an extra rendering step just for your JavaScript. An example would be: function logBoxHeight() { box.classList.add('super-big'); console.log(box.offsetHeight); // Forces the browser to re-render *now* } Verdict: Make sure you...
...always first read, then write style-relevant values. How to debug: Chrome shows warning icons in the event list in the Timeline for scripts that cause layout trashing. Performance issue...
...of a Linux process, like so: $ faketime 'last Friday 4 pm' date Fr 12. Sep 16:00:00 CEST 2025 However, we cannot just modify the time of the docker...
...need to affect the command being run inside the image. So we need to smuggle faketime into the container somehow, and activate it for the process being run.
...to be done separatly for each node version on your system, though. Install yarn 1 system-wide via apt The yarn package depends on the nodejs debian package, but with...
curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | gpg --dearmor | sudo tee /etc/apt/keyrings/yarn.gpg >/dev/null echo "deb [signed-by=/etc/apt/keyrings/yarn.gpg] https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list sudo apt-get update...
Static error pages To add a few basic styles to the default error pages in Rails, just edit the default templates in public, e.g. public/404.html. A limitation to these default...
...templates is that they're just static files. You cannot use Haml, Rails helpers or your application layout here. If you need Rails to render your error pages, you need...
...Adding Records via XHR and JS Example For the following examples we use a simple data model where a user has zero or more tasks. class ExampleMigration < ActiveRecord::Migration...
...user.tasks.build } end def update load_user @user.attributes = user_params if @user.save flash[:notice] = 'User saved successfully.' redirect_to(edit_variant_1_user_path(@user)) else flash[:notice] = 'User could not...
In SQL, NULL represents an "unknown" value. Because of this, it does not behave like a standard piece of data when used in comparison operators. If you don't account...
If you attempt to update or filter these users using a standard toggle, you might run the following queries: SELECT * FROM users WHERE name = 'Alice';
To make CSS rules dependent on the screen size, we use media queries: @media (max-width: 500px) { // rules for screen widths of 500px or smaller } Browsers will automatically enable and...
...disable the conditional rules as the screen width changes. To detect responsive breakpoints from JavaScript, you may use the global matchMedia() function. It is supported in all browsers:
I frequently find myself needing a combination of group_by, count and sort for quick statistics. Here's a method on Enumerable that combines the three: module Enumerable
group_by(&block) .transform_values(&:count) .sort_by(&:last) .to_h end end Just paste that snippet into a Rails console and use #count_by now! Usage examples...
There is an option you can set so that when using the cd command, small typos are automatically corrected. Add the following to your ~/.bashrc: # cd: autocorrect small typos and...
shopt -s cdspell Example: cd Porjects # Projects pwd # /home/judith/Projects Also, I recommend adding aliases for your most common typos of commands you regularly use to your ~/bashrc...
...that matter) will not be affected by this. If you define them in your specs, they will exist globally. This is because of how RSpec works (short story: instance_eval...
# ... end let(:record) { TestRecord.new }
end # TestRecord will exist here, outside of the spec! Do not do this. It will bite you eventually. For example, when you try to...
If you are using our opscomplete.com hosting we can set all environment variables mentioned below for your deployment on request. If you're lucky DO_NOT_TRACK=1 opts...
...are collecting data only after you opt into that. ng analytics --global disable Storybook https://storybook.js.org/docs/configure/telemetry npm run storybook -- --disable-telemetry npm run storybook -- --disable-crash-reports export STORYBOOK...
...T06:22:17.484221 #2698200] INFO -- : [53a240c1-489e-4936-bbeb-d6f77284cf38] more Goal When searching through Rails logs on production, it's often hard to see all lines that belong to...
...the same requests, since output of different requests is often interwoven. Instead, we want to find all requests that match a pattern, and then print all lines that share the...
...for DOM elements, there are some footguns you should know about. Some lists are synchronized with the DOM Some DOM APIs return live lists that automagically update their contents as...
...reflects the change automatically: document.querySelector('#two').remove() console.log(liveList) // [#one] console.log(nonLiveList) // [#one, #two] Snapshotting a live list Lists that silently change their elements can be very surprising to work...
...forget that bad resolution: git rerere forget your_file.rb Afterwards, the badly resolved file will still be in your working directory. To get it back with confict markers, say:
Rails wraps your parameters into an interface called StrongParameters. In most cases, your form submits your data in a nested structure which goes hand in hand with the strong parameters...
...However, there are cases where this does not fit your use case, or has side effects. If you do it differently, be extra careful not to introduce security issues.