Rails: Output helpers for migrations
When you're writing migrations that do more than changing tables (like, modify many records) you may want some output. In Rails > 3.1 you have two methods at hand: announce and say_with_time.
In the migration:
class AddUserToken < ActiveRecord::Migration
class User < ActiveRecod::Base; end
def up
add_column :users, :token, :string
announce "now generating tokens"
User.find_in_batches do |users|
say_with_time "For users ##{users.first.id} to ##{users.last.id}" do
users.each do |user|
...
Font sizing with rem - Snook.ca
CSS3 comes with new unit rem. It works like em but it is always relative to the <html> element instead of the parent element.
rem units are supported by all browsers and IE9+.
Git & Mac: Working with Unicode filenames
I had some problems with Git and the file spec/fixtures/ČeskýÁČĎÉĚÍŇÓŘŠŤÚŮÝŽáčďéěíňóřšťúůýž. After pulling the latest commits, it would show that file as untracked, but adding and committing it would throw error: pathspec 'check in unicode fixture file once again' did not match any file(s) known to git.
Solution
Install Git version > 1.8.2 using homebrew and set
git config --global core.precomposeunicode true
Done.
Reason
According to the linked Stackoverflow post ...
... the cause is the different im...
Testing shared traits or modules without repeating yourself
When two classes implement the same behavior (methods, callbacks, etc.), you should extract that behavior into a trait or module. This card describes how to test that extracted behavior without repeating yourself.
Note that the examples below use Modularity traits to extract shared behavior. This is simply because we like to do it that way at makandra. The same techniques apply for modules and overriding self.included.
Example
---...
Render a view from a model in Rails
In Rails 5 you can say:
ApplicationController.render(
:template => 'users/index',
:layout => 'my_layout',
:assigns => { users: @users }
)
If a Request Environment is needed you can set attributes default attributes or initialize a new renderer in an explicit way (e.g. if you want to use users_url in the template):
ApplicationController.renderer.defaults # =>
{
http_host: 'example.org',
https: false,
...
}
...
Rails: Disable options of a select field
Simply give the select helper an option :disabled, passing either a single value or an array. You need to specify the option's value, not its text.
= form.select :country, Address.countries_for_select, :include_blank => true, :disabled => ['disabled-value1', 'disabled-value-2']
Also see Cucumber: Check if a select field contains a disabled option on how to test this.
exception_notification 3.0.0+ lets you send errors as HTML e-mails
Exception notifications contain a lot of information: Backtraces, HTTP headers, etc. exception_notification tries its best to format this wall of information using ASCII art, but you can also make it send those notification as simple HTML e-mails that have some simple formatting for clarity, but no images etc. To do so, activate this option:
:email_format => :html
Those HTML notifications are still delivered with a text-only version, so if you are using a console cli...
Speed up your websites: Put JavaScripts at bottom
For websites that don't do JavaScript rendering on the client, it's best practice to put script tags at the bottom of the HTML. This way, the page can start to render before scripts have been loaded and run.
The caveat is that you also have to move all other script tags from your views to the bottom of the page. This can be done with helpers.
How to implement
- Add the attached javascript_helper to your app.
- Move your `javascript_i...
Sprites with Compass
Using CSS sprites for background images is a technique for optimizing page load time by combining smaller images into a larger image sprite.
There are ongoing arguments on how useful this still is, as modern browsers become more comfortable to load images in parallel. However, many major websites still use them, for example amazon, [facebook](...
iOS 5 "position: fixed" and virtual keyboard issues
The ipad onscreen keyboard changes position:fixed style to position:static that misplaces those elements and you'll have problems on each page with a form, e.g. search field.
There are several workarounds/hacks but no straight forward fix yet. Expect additional expense.
Live CSS / view reloading
Next time you have to do more than trivial CSS changes on a project, you probably want to have live CSS reloading, so every time you safe your css, the browser updates automatically. It's pretty easy to set up and will safe you a lot of time in the long run. It will also instantly reload changes to your html views.
Simply follow the instructions below, taken from blog.55minutes.com.
Install CSS live reload (only once per project)
- Add th...
Common mistakes when storing file uploads with Rails
1. Saving files to a directory that is not shared between deploys or servers
If you save your uploads to a made up directory like "RAILS_ROOT/uploads", this directory goes away after every deploy (since every release gets a new). Also this directory is not shared between multiple application servers, so your uploads are randomly saved to one local filesystem or another. Fixing this afterwards is a lot of fun.
Only two folders are, by default, shared between our application servers and deployments: "RAILS_ROOT/storage" and `"RAILS...
Help me, there is a zombie process!
Here is a good explanation for zombie processes.
Quote:
If you have zombie processes it means those zombies have not been waited for by their parent (look at PPID displayed by ps -l).
You have three choices: Fix the parent process (make it wait); kill the parent; or live with it.
Remember that living with it is not so hard because zombies take up little more than one extra line in the output of ps.
On a server I want to get informed if there are zombie processes and track them wi...
Clean up application servers when deploying
Our development process makes us deploy very often. As the number of releases grows, junk clogs up the hard drive of our application servers:
- Old release code
- Old
tmpfolders with compiled view templates etc. - Precompiled assets (Javascripts, images...) that no longer exist. When using the asset pipeline, Capistrano will symlink the
public/assetsdirectory toshared/assets. This is cool since we can still serve previous assets after a new release, in the window where browser caches might still have references to old assets. But i...
How to remap keys in Ubuntu
Good article that tells you how to change behavior of certain keys via xmodmap (with the help of exv if you need to find out the keycode).
Redactor WYSIWYG html editor
New WYSIWYG editor that claims to be lighter and prettier than TinyMCE and CKEditor. Has some Rails integration, too.
Ruby Scripts: Select the Ruby version in the shebang
As Bill Dueber has on his blog, you can call rvm in the shebang to select a Ruby version like this:
#!/usr/bin/env rvm 1.9 do ruby
Standard arguments to do apply, see $> rvm help do.
How to: Build a "generic observer" widget for the awesome window manager
If you want a widget for awesome that runs a command regularly (every X seconds) and puts the output into your awesome panel, this is for you.
Put the code below into your ~/.config/awesome/rc.lua. It supplies two methods:
-
execute_commandwill run a command and return its output. Multiple lines will be joined into one line. The code is from the awesome wiki. -
widget_with_timeoutis a method that takes a command to run and a timeout in secon...
Inherit without Single-Table-Inheritance (STI) in ActiveRecord
You have multiple options:
- Just don't have a
typecolumn. All STI magic will be disabled automatically. - If you have a
typecolumn but want to use it for something else (WAT?), you can setself.inheritance_column = :_non_existing_columnin the class definition - (Untested) In the parent class, set
self.abstract_class = true
This technique is useful to implement form models / presenters, where you want all the goodness of Ac...
How to find out which type of Spec you are
When you need to find out in which kind of spec you are during run-time, it's definitely possible. It's a lot easier in RSpec 2+.
For example, consider this global before block where you'd want to run some code for specific specs only:
config.before do
# stuff
that_fancy_method
# more stuff
end
RSpec 2+
If you want to run such a block for a specific type of specs, you can use filters:
config.before do
# stuff
# more stuff
end
config.before :type =...
AngularJS: Access the scope for a rendered DOM element
This trick might be useful to implement more complicated directives in AngularJS. I needed it to do drag'n'drop in a hierarchical tree.
Let's say you have this $scope in your Angular controller:
$scope.tasks = [
{ 'text': 'Task 1' },
{ 'text': 'Task 2' }
]
And you have this template:
<ul ng-repeat="task in tasks">
<li>
{{task.text}}
</li>
</ul>
Which renders this HTML:
<ul>
<li>Task 1</li>
<li>Task 2</li>
</ul>
If you'd like to access the scope bound to the second <li> you can say this in jQ...
How to not die with ActionView::MissingTemplate when clients request weird formats
When HTTP clients make an request they can define which response formats they can process. They do it by adding a header to the HTTP request like this:
Accept: application/json
This means the client will only understand JSON responses.
When a Rails action is done, it will try to render a template for a format that the client understand. This means when all you are HTML templates, a request that only accepts application/json will raise an error:
An ActionView::MissingTemplate occurred in pages#foo:
Missing templa...
Good real world example for form models / presenters in Rails
We have often felt the pain where our models need to serve too many masters. E.g. we are adding a lot of logic and callbacks for a particular form screen, but then the model becomes a pain in tests, where all those callbacks just get in the way. Or we have different forms for the same model but they need to behave very differently (e.g. admin user form vs. public sign up form).
There are many approaches that promise help. They have many names: DCI, presenters, exhibits, form models, view models, etc.
Unfortunately most of these approaches ...
How to write complex migrations in Rails
Rails gives you migrations to change your database schema with simple commands like add_column or update.
Unfortunately these commands are simply not expressive enough to handle complex cases.
This card outlines three different techniques you can use to describe nontrivial migrations in Rails / ActiveRecord.
Note that the techniques below should serve you well for tables with many thousand rows. Once your database tables grows to millions of rows, migration performance becomes an iss...