Adventures with Ruby

Rails 3 is coming. All the big changes are spoken of elsewhere, so I’m going to mention some small changes. Here are 3 random new methods added to ActiveSupport:

presence

First up is Object#presence which is a shortcut for Object#present? && Object. It is a bit of a sanitizer. Empty strings and other blank values will return nil and any other value will return itself. Use this one and your code might be a tad cleaner.

"".presence # => nil
"foo".presence #=> "foo"

# without presence:
if params[:foo].present? && (foo = params[:foo])
  # ..
end

# with presence:
if foo = params[:foo].presence
  # ...
end

# The example Rails gives:
state = params[:state] if params[:state].present?
country = params[:country] if params[:country].present?
region = state || country || 'US'
# ...becomes:
region = params[:state].presence || params[:country].presence || 'US'

I like this way of cleaning up you’re code. I guess it’s Rubyesque to feel the need to tidy and shorten your code like this.

uniq_by

Another funny one is Array.uniq_by (and it sister-with-a-bang-method). It works as select, but returns only the first element from the array that complies with the block you gave it. Here are some examples to illustrate that:

[ 1, 2, 3, 4 ].uniq_by(&:odd?) # => [ 1, 2 ]

posts = %W"foo bar foo".map.with_index do |title, i|
  Post.create(:title => title, :index => i)
end
posts.uniq_by(&:title)
# => [ Post("foo", 0), Post("bar", 1) ] ( and not Post("foo", 2) )

some_array.uniq_by(&:object_id) # same as some_array.uniq

exclude?

And the final one for today is exclude? which is the opposite of include?. Nobody likes the exclamation mark before predicate methods.

# yuck:
!some_array.include?(some_value)
# better:
some_array.exclude?(some_value)

And it also works on strings:

# even more yuck:
!"The quick fox".include?("quick") # => false
# better:
"The quick fox".exclude?("quick") # => false

The full release notes of Rails 3 can be read here.

Yes, I’ve written another plugin for Rails. It’s about so called root tables. It seem to be making them often. I want a list with options to choose from and some easy way to manage that list, which is a tedious task. That’s why I made a plugin to do this for me.

What I have so far is:

• Automatic validations and relations
• Completely configurable, with sensible defaults
• A management interface
• Works with acts_as_list and supports drag and drop sorting
• I18n support

Read more

When using Rails 2.3 and Passenger, you can do yourself a favor by adding this line to config/silencers/backtrace_silencer.rb

Rails.backtrace_cleaner.add_silencer { |line| line =~ /^\s*passenger/ }

Saves you scrolling through the endless backtraces passenger gives you for free

PS. A colleague tweeted this lovely backtrace of a spring with grails error. I say: backtrace cleaner FTW!

In my previous post, I talked about making filters using named scopes. To summorize:

I like the method of using a named_scope and delegating to specified filters. This way, you can structure your filters properly and get clean URLs. Also, you can chain other named scopes to the filter.

If you find yourself making an administrative web application, with many tables and filters, here’s an example to make it a little more DRY.
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Suppose you have an index page with people and you want to have a series of neat filters to show a selection of people. For example only the people still alive of only the adults. How would one do that?

I like the method of using a named_scope and delegating to specified filters. This way, you can structure your filters properly and get clean URLs. Also, you can chain other named scopes to the filter.

This is an example of how I would do that.
Read more