Flowdock

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April 2, 2013 - (v1_8_6_287 - v1_9_3_392)
0 thanks

Passing in an Array instead of individual arguments

Pass in array instead of list

h = { "cat" => "feline", "dog" => "canine", "cow" => "bovine" }

keys_i_want = %w(cow cat)

h.values_at(*keys_i_want) #=> ["bovine", "feline"]
April 2, 2013 - (v3.0.0 - v3.2.13)
0 thanks

Use concat insted of joining collection explicitely

concat method will be useful to join the collection object from looping conditions.

arr = ["a", "b", "c"]
content_tag(:ul, :class => 'a class') do
  arr.each do |item|
  concat content_tag(:li, item)
end

And this will generate the html as shown below

<ul class="a class">
  <li>a</li>
  <li>b</li>
  <li>c</li>
</ul>
April 2, 2013 - (v1_9_3_392)
0 thanks

output GBK

‘I am 中国人’.encode(‘gbk’,‘utf-8’)

April 2, 2013
0 thanks

you need kconv

require ‘kconv’

then

“中国人民很行”.toutf8

March 29, 2013
0 thanks
March 29, 2013
0 thanks

Edge case

Have look how #between? handle adge case. It’s different from DateTime’s.

Date.yesterday.between?(Date.yesterday, Date.tomorrow)
=> true

Date.tomorrow.between?(Date.yesterday, Date.tomorrow)
=> true
March 27, 2013 - (>= v3.0.0)
0 thanks

When dealing with has_many through

The non-repeating primary key id must be used with find_in_batches.

  • User has many things

  • User has many socks through things

  • Sock has many things

  • Sock has many users through things

For the sake of argument, assume the first user has two socks and all other users have one sock. There are 1000 users in total and 1001 socks in total.

User.joins(:socks).count
=> 1001
agg = []
# Incorrect
User.joins(:socks).find_in_batches{|g| agg += g}
agg.count
=> 1000

Sock.joins(:users).count
=> 1001
agg = []
# Correct
Sock.joins(:users).find_in_batches{|g| agg += g}
agg.count
=> 1001
March 27, 2013 - (v3.0.0 - v3.2.13)
0 thanks
March 18, 2013
3 thanks

Beware - May cause performance issues

A serialized attribute will always be updated during save, even if it was not changed. (A rails 3 commit explains why: http://github.com/rails/rails/issues/8328#issuecomment-10756812)

Guard save calls with a changed? check to prevent issues.

class Product < ActiveRecord::Base
  serialize :product_data
end

bad

product = Product.first
product.save

good

product = Product.first
product.save if product.changed?
March 13, 2013
1 thank

Another Hash#without

Mange made me think, and I wanted to expand on his example with a small change.

class Hash
  def without(*keys)
    dup.without!(*keys)
  end

  def without!(*keys)
    reject! { |key| keys.include?(key) }
  end
end

h = { :a => 1, :b => 2, :c => 3 }
h.without(:a)      #=> { :b => 2, :c => 3 }
h #=> { :a => 1, :b => 2, :c => 3 }  

h.without(:a, :c)  #=> { :b => 2 }

h.without!(:a, :c) # { :b => 2 }
h #=> { :b => 2 }
March 5, 2013
0 thanks

Minor correction to Rubybull's examples?

Was your first example intended to be:

a=[11,22,31,224,44]
=> [11, 22, 31, 224, 44]
a.each.with_index { |val,index| puts "index: #{index} for #{val}" }
March 5, 2013 - (v3.0.0 - v3.2.8)
0 thanks

Exceptions raised within are ignored.

From http://guides.rubyonrails.org/active_record_validations_callbacks.html

The after_commit and after_rollback callbacks are guaranteed to be called for all models created, updated, or destroyed within a transaction block. If any exceptions are raised within one of these callbacks, they will be ignored so that they don’t interfere with the other callbacks. As such, if your callback code could raise an exception, you’ll need to rescue it and handle it appropriately within the callback.

March 1, 2013
0 thanks

Default field order

If you want to set an app wide default order for the fields (rather than passing :order each time), use the locale file.

eg. edit config/locale/en.yml to include:

en:
  date:
    order: 
      - :day
      - :month
      - :year
February 25, 2013 - (v1_9_3_125)
0 thanks

Using the undef/replace param overwrites the fallback parameter

If you want to provide a fallback Hash / Proc / Object you must not define the :undef and/or replace params since they overwrite the fallback.

How fallback works

fallback = Hash.new { '?' }
fallback["\u2014"] = "-"
"\u2014".encode!("ISO-8859-15", fallback: fallback)
=> "-"

Undef overwrites fallback:

fallback = Hash.new { '?' }
fallback["\u2014"] = "-"
"\u2014".encode!("ISO-8859-15", fallback: fallback, undef: :replace, replace: '?' )
=> "?"
February 25, 2013
0 thanks

Where did this go?

For Ruby 1.9 and later, use Kernel#Array to get this functionality.

February 23, 2013
0 thanks

Modes listed in IO class

See class IO for file open modes

February 22, 2013
0 thanks

Checking content_for

There’s a much simpler way to check if content exists or not, and it’s been provided as example in docs since 05.2010:

module StorageHelper
  def stored_content
    content_for(:storage) || "Your storage is empty"
  end
end

But this behavior was broken with SafeBuffer. You’ll be able to use it again when this issue (github.com/rails/rails/issues/9360) will be fixed and merged with master.

February 20, 2013
0 thanks

It also works with strings

It works with strings:

ActiveRecord::Base.connection.column_exists?('users', 'id')

Which is helpful if you need to specify the database/schema to use:

ActiveRecord::Base.connection.column_exists?('secondary.users', 'id')
February 20, 2013
0 thanks

Freezing Time.now

You’d be much better off using the Timecop gem ( rubygems.org/gems/timecop ) than than manually writing monkey-patches to freeze Time.now etc.

It also supports time travel (i.e. changing the time, but allowing the clock to continue running).

February 14, 2013 - (>= v3.2.8)
1 thank

conditional rescue from does not seem working on Rails 3.2.11

Be careful, conditional rescue_from does not work in Rails 3.2.11

February 8, 2013 - (>= v2.3.8)
0 thanks

The purpose of this method

This method keeps track of whether a hidden id field needs to be created when the form builder is generating fields for a nested model. It gets set to true by #hidden_field when that method is used to create a field named ‘id’.

Here’s an example of what this can be useful for: http://railsforum.com/viewtopic.php?id=39640

February 4, 2013
0 thanks

Your scope cannot be called &#x27;locked&#x27;

will cause intermittent problems of the type

undefined method 'locked' for #<Class:0x007fdab3025298>

Use something like ‘access_locked’ instead

February 3, 2013 - (v1_9_3_125)
0 thanks

How does enum#each_index differ from enum#with_each_index ?

Here is the working one each_with__index:

a=[11,22,31,224,44].each_with_index { |val,index| puts "index: #{index} for #{val}" if val < 30}
  index: 0 for 11
  index: 1 for 22
  => [11, 22, 31, 224, 44]

Below couldn’t produce the output, as with_index couldn’t work on the array.To make it workble, we need to first convert it to enumerator. And that can be done via the help of .to_enum, .each, or .map

a = [11,22,31,224,44].with_index { |val,index| puts "index: #{index} for #{val}" if val < 30}
=>NoMethodError: undefined method `with_index' for [11, 22, 31, 224, 44]:Array
       from (irb):2
       from C:/Ruby193/bin/irb:12:in `<main>'

Here is the working one with_index:

a = [11,22,31,224,44].each.with_index { |val,index| puts "index: #{index} for #{val}" if val < 30}
index: 0 for 11
index: 1 for 22
=> [11, 22, 31, 224, 44]
February 3, 2013 - (v1_9_3_125)
0 thanks

Difference between enum#with_object and enum#each_with_object

I found a very good post on SO - which clearly explained the difference between enum#with_object and enum#each_with_object. The link is as follows:

http://stackoverflow.com/questions/14671881/how-does-enumwith-object-differ-from-enumeach-with-object/14672305#14672305

February 2, 2013 - (v1_9_3_125)
1 thank

Enumerator#with_index has confusing documentation

Enumerator#with_index has confusing documentation, but hopefully this will make it clearer.

Code example

a=[11,22,31,224,44].to_enum
=> [11, 22, 31, 224, 44]
a.with_index { |val,index| puts "index: #{index} for #{val}" }
index: 0 for 11
index: 1 for 22
index: 2 for 31
index: 3 for 224
index: 4 for 44

a=[11,22,31,224,44].to_enum
=> #<Enumerator: [11, 22, 31, 224, 44]:each>
a.with_index(2){ |val,index| puts "index: #{index} for #{val}" if val > 30 }
index: 4 for 31
index: 5 for 224
index: 6 for 44
=> [11, 22, 31, 224, 44
February 2, 2013
0 thanks

Other Example

##

class Exam
 cattr_reader :code, :description, :points, :instance_reader => false

 @@code = "EXM"
 @@description = "Sent Exam"
 @@points = 1000
end

In this case it’s possible to use

Exam.code # => EXM
Exam.description # => Sent Exam
Exam.points # => 1000
January 29, 2013
0 thanks

Works also with Mongoid

What works for Active Record, also works for Mongoid:

de:
  mongoid:
    attributes:
      picture:
        explanation: Description
January 26, 2013 - (v3.0.0 - v3.2.8)
0 thanks

Use sqlite3, not sqlite

Note that typically if you want to connect to an SQLite database the adapter would be “sqlite3”; not “sqlite” as depicted in the documentation above. Just using the term “sqlite” might result in the error message: “database configuration specifies nonexistent sqlite adapter”

January 23, 2013 - (>= v3.0.0)
0 thanks

Using an unobtrusive Ajax (UJS) :onchange call to the controller#action

An :onchange call can be made using the Rails 3 jquery-ujs helper in the form:

check_box_tag( name, value, checked, html_and_other_options)

For example:

select_tag( "my_tag_id", entity.id,
  class: "progress bar update_msg", disabled: disabled?
  data: {
    remote: true,
    url: url_for( action: :my_controller_action, id: my_id)
    // application symbols
    progress_bar: "progress_bar_div_id",
    update: "message_div_id"
  }
)

The jquery_ujs looks for data-remote and data-url. These can be spelled-out or placed in the data hash. The url must be formed as select_tag does not call url_for, unlike some of the other related tags. Values for application symbols can also be passed through. jQuery triggers will work on the Ajax events that occur. This generates the following:

<input class="progress_bar update_msg" data-progress-bar="progress_bar_div_id" data-remote="true" data-update="message_div_id" data-url="/my_controller/my_controller_action/my_id" id="my_tag_id" name="my_tag_id" type="checkbox" value="4"/>

In this example, by tying into the events the program makes visible an existing hidden progress bar while awaiting a server response, and then displays a div containing a message returned by the server and hides the progress bar. If the div contains a class= for notice or error, then they will fade out.

$(".layout")
  .on('ajax:beforeSend', ".progress_bar", function(){ 
    // get id of element to make visible
    var progress_bar_id = '#' + this.getAttribute('data-progress-bar');
    $(progress_bar_id).show();
  })
  .on('ajax:complete', ".progress_bar", function(){ 
    // get id of element to hide
    var progress_bar_id = '#' + this.getAttribute('data-progress-bar');
    $(progress_bar_id).hide();
  })
  .on('ajax:complete', ".update_msg", function(evt, xhr, options){ 
    // get id of element to contain message
    var update = this.getAttribute('data-update'); 
    $("#" + update).replaceWith($(xhr.responseText).attr("id", update));
    // cause responses with these classes to fade away...
    $('.notice').fadeOut(2500);
    $('.error').fadeOut(8000);
  });