Updated: Minor caveat for minified Font Awesome fonts with webpack
I noticed that changing the subset of used icons does not change the file name of the generate font, and will cause issues with browser caching.
I've added a workaround.
Javascript: Comparing two arrays for equality
Don't Google this, you will lose all will to live. Instead use Object#isEqual from Lodash or Underscore.js:
_.isEqual([1, 2], [2, 3]) // => false
To compare two arrays for equality in a Jasmine spec assertion, see Jasmine: Testing complex types for equality.
How to create memory leaks in jQuery
jQuery doesn't store information about event listeners and data values with the element itself. This information is instead stored in the global $.cache object. Every time you add an event listener or data value to a jQuery object, $.cache gains another entry.
The only way that a $.cache entry gets deleted is when you call remove() on the element that put it there!
Since cache entries also have a pointer back to the element that spawned them, it is easy to create DOM elements that can never be garbage-collected.
Below are …
How to examine an unknown Ruby object
When debugging your application, you will come across objects created by some gem or framework. You don't have the source code at hand, still need to inspect this object. Here are some tools to do so:
Relevant methods
@object.methods - Object.instance_methods returns a list of methods excluding methods inherited from Object. This makes the methods list drastically more relevant. You can also try subtracting other base classes like ActiveRecord::Base.methods etc.
Filtering method list
@object.methods.grep /keyword/ comes…
Ruby tempfiles
Tempfiles get deleted automatically
With the the ruby Tempfile class you can create temporary files. Those files only stick around as long as you have a reference to those. If no more variable points to them, the GC may finalize the object at some point and the file will be removed from the filesystem. If you would try to access your tempfile then using its path (which you stored previously), you would get an error because the file no longer exists.
Unlink your tempfiles when you're done with them
-…
Updated: Sun Java JVM/JRE on Ubuntu Linux
- Added Java 10 installation guide
- Added an instruction how to change the default java version
Do not pass an empty array to ActiveRecord.where when using NOT IN
Be careful with the Active Record where method. When you accidentally pass an empty array to the where method using NOT IN, you probably will not get what you expected:
User.where("id NOT IN (?)", [])
=> SELECT `users`.* FROM `users` WHERE (id NOT IN (NULL))
Even though you might expect this to return all records, this actually results none.
Never use the expression id NOT IN (?) in any scope! See below some workarounds.
Rails < 4
Rails < 4 does not provide a pretty workaround.
```
ids = []
if ids.present?
Us…
Ruby: required keyword arguments in the pre-2.1 era
Starting with Ruby 2.0 you can define methods with keyword arguments.
In 2.1+ required keyword arguments can be defined by using a colon without default value:
def match(value, ignore:)
...
end
To accomplish something similar in ruby 1.8, use:
def match(value, options = {})
ignore = options.fetch(:ignore)
...
end
Updated: How Rails chooses error pages (404, 500, ...) for exceptions
Emphasized that changing the error mapping has nothing to do with "rescueing", and that error notification has to be muted on its own.
Defining class methods with Modularity traits
There are two ways to define a class method from a Modularity trait. Note that the usual caveats regarding class method visibility apply.
Using define_method
The recommended way is to define a method on your module's singleton class:
# ruby 1.9+
module SomeTrait
as_trait do
define_singleton_method :foo do
# ...
end
...