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June 12, 2009
0 thanks

Reusing shared examples

share_examples_for “a shape” do

   it "should have a color" do
     @shape.color.should == :black
   end
 end

describe "a circle" do
  before(:all) do
    @shape = Circle.new
  end 
  it_should_behave_like "a shape"
end
June 12, 2009
0 thanks

A stub with argument and return value

it “should use a dummy method with argument and return value” do

 dummy = mock("dummy").stub!(:emulate)
 dummy.should_receive(:emulate).with(:something).and_return("Done! sir!")
 dummy.emulate(:something).should == "Done! sir!"
end
June 12, 2009
1 thank

Conditions work for lower-level validate methods too

I don’t think this is mentioned in the docs anywhere, or else I couldn’t find it: Because validate, validate_on_create, and validate_on_update are ActiveSupport::Callbacks, their symbol forms support conditions just like validates_presence_of and company:

validate :permaname_must_be_unique, :if => :normal_entry?
validate_on_create :posted_at_must_be_valid_timestamp, :unless => Proc.new {|e| e.posted_at.nil? }
validate_on_update :title_must_not_contain_apostrophes, :if => :title_starts_with_a_b?
June 11, 2009
0 thanks

Not really helpful

When you’re trying to construct a specialized path name for a partial based on a record type you’re probably better off writing your own helper.

def topic_partial_path(topic)
  ['admin', topic.class.table_name, "#{topic.class.table_name.singularize}_as_topic"].join('/')
end
June 11, 2009
4 thanks

Keeping the flash object on multiple redirects

If your controllers are redirecting more than once, the flash contents will be lost. To avoid it, execute flash.keep before each redirection.

Check ActionController::Flash::FlashHash for more handy methods (discard, now, …)

June 11, 2009
2 thanks
June 10, 2009
2 thanks

[:a, :b, :c].try([1]) ? The answer is No.

Correct way is this:

[:a, :b, :c].try(:at, 1)
June 10, 2009
0 thanks

list of predefined variables

$! The exception information message set by ‘raise’. $@ Array of backtrace of the last exception thrown.

$& The string matched by the last successful pattern match in this scope. $` The string to the left of the last successful match. $‘ The string to the right of the last successful match. $+ The last bracket matched by the last successful match. $1 to $9 The Nth group of the last successful regexp match. $~ The information about the last match in the current scope.

$= The flag for case insensitive, nil by default. $/ The input record separator, newline by default. $\ The output record separator for the print and IO#write. Default is nil. $, The output field separator for the print and Array#join. $; The default separator for String#split.

$. The current input line number of the last file that was read. $< The virtual concatenation file of the files given on command line. $> The default output for print, printf. $stdout by default. $_ The last input line of string by gets or readline.

$0 Contains the name of the script being executed. May be assignable. $* Command line arguments given for the script sans args. $$ The process number of the Ruby running this script. $? The status of the last executed child process. $: Load path for scripts and binary modules by load or require.

$“ The array contains the module names loaded by require. $DEBUG The status of the -d switch. $FILENAME Current input file from $<. Same as $<.filename. $LOAD_PATH The alias to the $:. $stderr The current standard error output. $stdin The current standard input. $stdout The current standard output. $VERBOSE The verbose flag, which is set by the -v switch. $-0 The alias to $/. $-a True if option -a (”autosplit“ mode) is set. Read-only variable. $-d The alias to $DEBUG. $-F The alias to $;. $-i If in-place-edit mode is set, this variable holds the extension, otherwise nil. $-I The alias to $:. $-l True if option -l is set (”line-ending processing“ is on). Read-only variable. $-p True if option -p is set (”loop“ mode is on). Read-only variable. $-v The alias to $VERBOSE. $-w True if option -w is set.

Source: http://en.wikibooks.org/wiki/Ruby_Programming/Syntax/Variables_and_Constants#Pre-defined_Variables

June 10, 2009 - (v1.0.0 - v2.3.2)
5 thanks

Have the check_box checked by default

To have the check box checked by default, pass either :checked => true or :checked => 'checked' in the options. See ActionView::Helpers::InstanceTag#to_check_box_tag for details.

June 8, 2009 - (v2.2.1 - v2.3.2)
5 thanks

This is ON by default in :has_many

When defining a has_many relationship this behaviour is on by default. See has_many documentation, look for the :validate flag.

June 6, 2009
8 thanks

add index with :quiet=>true option for indices that are possibly already added

# Allows you to specify indices to add in a migration that will only be created if they do not # already exist, or to remove indices only if they already exist with :quiet=>true module ActiveRecord::ConnectionAdapters::SchemaStatements

def add_index_with_quiet(table_name, column_names, options = {})
  quiet = options.delete(:quiet)
  add_index_without_quiet table_name, column_names, options
rescue
  raise unless quiet and $!.message =~ /^Mysql::Error: Duplicate key name/i
  puts "Failed to create index #{table_name} #{column_names.inspect} #{options.inspect}"
end
alias_method_chain :add_index, :quiet

def remove_index_with_quiet(table_name, column_names, options = {})
  quiet = options.delete(:quiet)
  raise "no options allowed for remove_index, except quiet with this hack #{__FILE__}:#{__LINE__}" unless options.empty?
  remove_index_without_quiet table_name, column_names
rescue
  raise unless quiet and $!.message =~ /^Mysql::Error: Can't DROP/i
  puts "Failed to drop index #{table_name} #{column_names.inspect}"
end
alias_method_chain :remove_index, :quiet

end

June 4, 2009
2 thanks

A typical usage for a mock

You want to use a mock when you’re testing a behaviour of one of your methods that interacts with some outside world service (eg. an FTP server).

it "should login to ftp server" do
  ftp = mock('Ftp server', :null_object => true)
  Net::FTP.should_receive(:new).and_return(ftp)
  ftp.should_receive(:login).with('username', 'password')
  some_obj.connect
end

def connect
  session = Net::FTP.new('server.com')
  session.login('username', 'password')
  session.close
end
June 4, 2009
5 thanks

A catch-all format

If you’d like to specify a respond_to only for 1 or a few formats and render something else for all other formats, eg: (action.rss returns a feed but action.html or action.js should just render 404), use format.all:

respond_to do |format|
  format.rss { render_rss }
  format.all { render_404 }
end

Rails will render an empty string for all formats that don’t specify a response explicitly.

June 4, 2009
2 thanks

example

Ruby style

Dir[File.join(RAILS_ROOT, 'vendor', 'plugins', '*')]

Rails style

Dir[Rails.root.join('vendor', 'plugins', '*')]
June 4, 2009 - (v2.3.2)
1 thank

Security hole in 2.3.2

This method has a security hole in Rails 2.3.2. See http://weblog.rubyonrails.org/2009/6/3/security-problem-with-authenticate_with_http_digest for explanation.

Rails 2.3.3 should fix the problem.

June 3, 2009
7 thanks

ActiveRecord::RecordNotSaved can be triggered by accidental false return values in callbacks

You may have this exception raised if any of the defined callbacks such as ActiveRecord::Base#before_save or ActiveRecord::Base#before_create return false.

This can happen accidentally. For example:

class MyModel < ActiveRecord::Base
  before_save :assign_default_foo

protected
  def assign_default_foo
    self.foo = false
  end
end

Since assign_default_foo leaves a false value on the stack, the model will not be saved. A way around this is to simply leave nil or an empty return instead:

class MyModel < ActiveRecord::Base
  before_save :assign_default_foo

protected
  def assign_default_foo
    self.foo = false
    nil
  end
end
June 3, 2009 - (<= v2.3.2)
0 thanks

multi scope to sql

validates_uniqueness_of :name, :scope => [:big_category_id, :small_category_id]

SELECT * FROM schedules WHERE (products.name = 'xxxx' AND products.big_category_id= 1 AND products.small_category_id = 1) LIMIT 1
June 2, 2009 - (v2.2.1 - v2.3.2)
1 thank

Do not create an [ ] method

I created a helper method to access some meta data using

def [](name)
  # do stuff
end

This breaks ActiveRecord behaviors. all belongs_to relations were broken

eg.

class Image
  belongs_to :album
end

i = Image.find :first
i.album_id # 1
i.album # nil

Album.find 1 # works

If you experience this behavior, you probably created a method that breaks the default systematics (like I did with the [ ] method)

June 1, 2009
1 thank

Shared examples

Use it together with share_examples_for like this:

share_examples_for "a shape" do
  it "should have a color" do
    # ...
  end

  it "should have a center point" do
    # ...
  end
end

describe "a circle" do
  it_should_behave_like "a shape"

  it "should be round" do
    # ...
  end
end
June 1, 2009 - (v2.2.1 - v2.3.2)
2 thanks

Further To: Memoize will not cache singleton methods

er…it will:

Code example

class PersonType < ActiveRecord::Base
  class << self
    # Add the mixin here:
    extend ActiveSupport::Memoizable
    def mister
      find_by_name('Mister')
    end
    memoize :mister
  end
end
June 1, 2009
0 thanks

Typical stub! usage

Typically you would call

my_object.stub!(:updated_at).and_return(time_object)
June 1, 2009
2 thanks

Make sure your action names don't step on any toes.

In my experience, if you ever have a controller action named “process”, your controller will cease to function, as there is both a class and instance method called process in ActionController::Base.

There are undoubtedly other action names that will cause conflicts, but this one is particular I’ve run into a number of times.

May 31, 2009
2 thanks

You can call several times

You can call it several times, like:

class Comment < ActiveRecord::Base
  validate :must_be_friends
  validate :must_be_awesome
  ...

or with several arguments:

class Comment < ActiveRecord::Base
  validate :must_be_friends, :must_be_awesome
  ...
May 27, 2009
0 thanks

Potentially slow operation

Remember that checking for a value is a potentially slow operation (all the elements might be iterated) as oposed to querying a key (e.g. with has_key?), which is supposed to be fast in a Hash.

May 27, 2009 - (>= v1_8_6_287)
2 thanks

map_with_index

If you want to access the element index when using map, you can do it with enum_for:

(1..6).enum_for(:each_with_index).map { |v, i| "index: #{i} value: #{v}" }
#=> ["index: 0 value: 1", "index: 1 value: 2", "index: 2 value: 3", "index: 3 value: 4", "index: 4 value: 5", "index: 5 value: 6"]
May 26, 2009
1 thank

Potentially slow operation

Remember that checking for a value is a potentially slow operation (all the elements might be iterated) as oposed to querying a key (e.g. with has_key?), which is supposed to be fast in a Hash.

May 22, 2009
0 thanks

Alternative Way to Handle

This plugin may also help solve the problem from the model side.

http://github.com/rxcfc/multi_assignment_sanity