Recent notes

To use class attribute with a hash

You can use a setter with merge:

self.settings = settings.merge(key => value)

On destroying data

Reply to tvle83 and pgmcgee: the destructiveness of this method depends on your database. Some databases are better at converting between disparate types than others. For example, when changing a column from a numeric type to a string type, some databases drop the data where others will turn the numbers into their string representations.

Essentially, YMMV.

What it do?

For those favoring YAML outputs, this methods simply and recursively outputs the keys and values in YAML (into a String) for your pleasure.

a misprint?

In section ‘Bi-directional associations’ an example:

d = Dungeon.first

t = d.traps.first

d.level == t.dungeon.level # => true

d.level = 10

d.level == t.dungeon.level # => false

Then use has_many associations, but lower than written ‘for belongs_to associations has_many inverse associations are ignored.’

rest of code is in Object#try

The logic for #try is shared between this method and Object#try – “Show source” here doesn’t show the whole story. Both methods are currently implemented in the file activesupport/lib/active_support/core_ext/object/try.rb .

rest of code is in NilClass#try

If you click “Show source” here, you may get confused. The logic for #try is shared between this method and NilClass#try . Both versions are currently implemented in the file activesupport/lib/active_support/core_ext/object/try.rb .

Long-wanted functional extension

This is pretty nice method allowing you to build stuff in a functional way.

Lets say you want to build a hash from an array, keyed by array object, where each value is the number of same objects in the array.

# imperative style :-P

h = Hash.new(0)
[1, 3, 2, 3, 1, 3].each { |i| h[i] += 1 }
h # => {1=>2, 3=>3, 2=>1} 

# functional style, using inject. Note that you need to explicitly return the accumulator in the end

[1, 3, 2, 3, 1, 3].inject(Hash.new(0)) { |a, i| a[i] += 1; a } 
# => {1=>2, 3=>3, 2=>1} 

# using each_with_object. Note the reversed block params - accumulator is the last parameter. 
# Mnemonic: consistent with each_with_index, where object is the first parameter

[1, 3, 2, 3, 1, 3].each_with_object(Hash.new(0)) {|i, a| a[i] += 1}
# => {1=>2, 3=>3, 2=>1} 

Replacement

Replacement

# Method using returning can replaced
def foo
  returning Hash.new do |h|
    h[:foo] = "bar"
  end
end
# By method using tap  
def foo
  Hash.new.tap do |h|
    h[:foo] = "bar"
  end
end

Skipping validation - follow up

For Rails 2.x use #save(false) for Rails 3.x use #save(:validate => false)

Set ids when using a collection of values (cont.)

Regarding schmidt’s post.

The following will not have the expected behavior:

<% Car.each do |c| %>
  <%= check_box_tag "car_ids[]", c.id, :id => "car_ids_#{c.id}" %>
<% end %>

But, if you put the “checked” option to false (or true), it will.

<% Car.each do |c| %>
  <%= check_box_tag "car_ids[]", c.id, false, :id => "car_ids_#{c.id}" %>
<% end %>

Changing the Message

For Change the default message:

Code example

validates :invoice_number, :presence => {:message => 'The invoice number must be informed.'}

Assignment using 'key: value'

Another shorthand way of assigning key, value pairs:

Hash[one: 1, two: 2] #=> {:one=>1, :two=>2}

conditional rescue_from

Would it be possible to do something like:

rescue_from Exception, :with => my_handler, :unless => request.local?

Checking content_for

@tordans You asked your question 3 years ago, but in any case, should anyone have that same issue, you can manage that with:

- unless content_for(:footer).blank?
  yield(:footer)
- else
  == render "layouts/footer_big"

content_for(:x) defaults to an empty string, that’s why you need to check for blank? not nil?.

this has been deprecated; see linked note

This has been deprecated. See this note on memoize : http://apidock.com/rails/ActiveSupport/Memoizable/memoize#1317-this-has-been-deprecated-replace-with-Memoist

this has been deprecated; replace with Memoist

In Rails 3.2, memoize has been deprecated. In edge Rails, it has been removed.

The commit when it was deprecated: http://github.com/rails/rails/commit/36253916b0b788d6ded56669d37c96ed05c92c5c

A Stack Overflow question about this change: http://stackoverflow.com/q/9132197/578288

I personally disagree with the removal of memoize, and don’t recommend using the `||=` pattern Rails now suggests. The exception is if your entire program only memoizes something once or twice, so it’s not worth including a gem for.

The easiest way to keep using memoize is to use the Memoist gem (http://github.com/matthewrudy/memoist , http://rubygems.org/gems/memoist), which is a simple extraction of ActiveSupport::Memoizable into its own gem.

see also – similar methods

See also DateTime#strftime and Date#strftime . (They work similarly, but have different APIdock notes.)

see also – similar methods

See also Time#strftime and DateTime#strftime . (They work similarly, but have different APIdock notes.)

see also – similar methods

See also Time#strftime and Date#strftime . (They work similarly, but have different APIdock notes.)

Adding Additional Parameters to form_for

If you want to add additional parameters to the form_for helper, but still want to use one form for both your “create” and your “update” actions, you can add the additional parameters to the :url option, but you need to omit the :controller and :action keys.

form_for(@user, :url => {:param1 => "value1", :param2 => "value2"}) do |f|

or

form_for([@post, @comment], :url => {:param1 => "value1", :param2 => "value2"}) do |f| 

where param1 and param2 are not :controller or :action

Test if an array is included in another

Array

class Array
   def included_in? array
     array.to_set.superset?(self.to_set)
   end
end

[1,2,4].included_in?([1,10,2,34,4]) #=> true

Another usage example

given: order active record class with “state” string field

class Order < ActiveRecord::Base
  def state
    @state ||= ActiveSupport::StringInquirer.new(read_attribute(:status))
  end
end

order = Order.new(state: "initial")
order.state.initial? #=> true
order.state.paid? #=> false

add_to_base in Rails 3

In addition to stevo’s note, in Rails 3 you can also do:

model_instance.errors.add(:base, "Msg") 

Month-first date string no longer parses correctly

The following date format won’t be parsed correctly:

'06/15/2008'.to_date 

Use this instead:

Date.strptime("6/15/2012", '%m/%d/%Y')

Example of usage

e.g.

str = ActiveSupport::StringInquirer.new('test')

str.test? # => true
str.foobar? # => false

more_than? instance method

Over the weekend I kept running into instances where I was writing code like this:

Code example

arr = ['hello', 'world']

if arr.length > 2
 # do stuff
else
 # do something else
end

So I ended up extending the core and adding an instance method of more_than?

Code example

class Array
  def more_than?(num)
    length > num
  end
end

Usage

arr = ['hello', 'world']
puts "Hello" if arr.more_than? 1

:disable_with is deprecated

Or you can use this way:

<%= submit_tag "Login", data: { disable_with: "Please wait.." } %>

:disable_with is deprecated

Since version 3.2.5 you should not use :disable_with.

Use this:

<%= submit_tag "Login", 'data-disable-with' => "Please wait.." %>

You can remove leading Zeros this way as well

By just adding a - symbol.

%-I %-d

This method does not work.

It’s an old problem, reported back in 2010, just reopened issue:

http://github.com/rails/rails/issues/6620