28 Jul 2014
I wanted to setup ruby source code on my machine. The
source on Github has detailed
instructions on how to do the setup.
git clone github.com/ruby/ruby
cd ruby
autoconf
./configure
make
make install
worked correctly on Mac OS X and Ruby was installed in
usr/local/bin.
I use rbenv for managing Ruby versions. After setting up the Ruby from
source, i wanted to use it using rbenv. Why? It will make very easy to
switch between dev version and normal version. rbenv shell ruby-dev,
do something, make some changes, compile again, test again. rbenv
shell 2.1.2, and back to normal.
But as the source Ruby was installed in usr/local/bin, rbenv was not
able to find it.
I asked question on #ruby on IRC and Postmodern pointed me to
this.
It mentions passing --prefix option to the ./configure command.
We can pass the name of directory where we want to install Ruby to
this option.
So we can run
./configure --prefix=PATH_TO_INSTALL_RUBY
rbenv by default, installs all rubies in ~/.rbnev/versions
And when we do rbenv versions, it looks for all rubies installed in
this directory and lists them.
The content of my ~/.rbnev/versions directory looked like these:
prathamesh ~/.rbenv/versions 2.0.0
$ ls
2.0.0-p247 2.0.0-p353 2.0.0-p481 2.1.0 2.1.1 2.1.2 rbx-2.2.6
prathamesh ~/.rbenv/versions 2.0.0
Now if we give prefix path to configure command, the dev-ruby will be
installed in ~/.rbenv/versions
./configure --prefix="$HOME/.rbenv/versions/ruby-dev"
After make and make install, dev ruby was installed in
~/.rbnenv/versions in ruby-dev directory.
Now rbenv versions output had ruby-dev also.
prathamesh ~/.rbenv/versions 2.0.0
$ rbenv versions
* system (set by /Users/prathamesh/.rbenv/version)
2.0.0-p247
2.0.0-p353
2.0.0-p481
2.1.0
2.1.1
2.1.2
rbx-2.2.6
ruby-dev
prathamesh ~/.rbenv/versions 2.0.0
As ruby-dev is listed by rbenv versions, i can switch to it easily:
Update
On Mac OS X Sierra, I had to also pass the flag for openssl directory while configuring.
cd ruby
make clean
./configure --prefix="$HOME/.rbenv/versions/ruby-dev" --with-opt-dir="/usr/local/opt/openssl/"
make
make install
This sets up Ruby dev version on my machine and also allows me to
switch back and forth using rbenv.
23 Jul 2014
Recently i was bitten by this weirdness of BigDecimal in Ruby.
BigDecimal.new excepts initial value and number of significant
digits. In one of my app, BigDecimal.new was called with string
initial value without precision. Everything was working great and
suddenly something changed. And this error started coming.
can't omit precision for a Float.
What happened was, the value passed to BigDecimal.new was no longer
string. Due to some changes in other parts of code, float was passed
to BigDecimal.new.
Now when a float or rational is passed to BigDecimal.new, it
requires precision to be present. Otherwise raises error.
can't omit precision for a Float(/Rational).
Fix was very simple. Pass the precision digits as second argument to
the BigDecimal.new call.
20 Jul 2014
I was trying to setup flyspell mode on new Mac and whenever i do
but Emacs was throwing error -
Problem - Flyspell does not work with Emacs. Can't find ispell.
Mac OS X does not come with ispell or its replacement aspell.
So the first thing is to install aspell using brew.
Now to tell emacs to use aspell instead of ispell.
(setq ispell-program-name "aspell")
Problem
Even though, aspell is installed properly, Emacs is not able to find
it in the path.
Solution
Instead of just aspell, specify the full path to the aspell
executable.
(setq ispell-program-name "/usr/local/bin/aspell")
There were other solutions mentioned on the internet like updating the
PATH env variable and exec-path variable with usr/local/bin but
it did not work for me.
23 Feb 2014
Devise allows us to customize after_signup_path by overriding a
protected method in RegistrationsController.
class RegistrationsController < Devise::RegistrationsController
protected
def after_inactive_sign_up_path_for(resource)
your_custom_path
end
def after_sign_up_path_for(resource)
your_custom_path
end
end
If we are using :confirmable with devise, sometimes we need to show
user a message -
Confirmation email has been sent to you <user_email>.
Please confirm your email.
Lets say that route name for this is confirmation_email_sent_path.
class RegistrationsController < Devise::RegistrationsController
protected
def after_inactive_sign_up_path_for(resource)
confirmation_email_sent_path
end
end
Now how to pass user’s email to this path?
One way is to override create action of Devise’s
RegistrationsController. But this is bad as we will get dependent on
current Devise implementation.
Lets see how we can achieve this with minimum dependency.
resource has the User object. So we can use that to pass user’s
email to the confirmation_email_sent action.
class RegistrationsController < Devise::RegistrationsController
protected
def after_inactive_sign_up_path_for(resource)
confirmation_email_sent_path(email: resource.email)
end
end
Now we can access this email in confirmation_email_sent action.
def confirmation_email_sent
@email = params[:email]
end
19 Jan 2014
We sent newsletter campaigns from our Rails app. One of the main
requirement of such campaign is how many emails bounced?. We need to
track all bounced emails and map them again to a specific campaign
because there will be multiple campaigns going on all the time.
To track bounced emails efficiently, we need to set unique return path
for every recipient. This technique is called Variable Envelope Return
Path or VERP
Postfix supports VERP with -V switch. For eg.
sendmail.postfix -V -f bounced
will generate return path for anyone@example.com as
bounced+anyone=example.com@yourdomain.com.
If you want more control and more information like from which campaign
this email was sent, we need to send more information in the return-path.
So it is best to generate our own return path pattern and parse it
once it is received. We generated a pattern where return-path will
generated from all the required information for tracking.
This pattern was given to mail method as follows:
mail(
from: 'hello@example.com',
to: 'client@example.com',
return_path: generate_verp_pattern
)
So now the first problem was solved. We were sending unique
return-path for every email that was going out from the system.
Next part is to track it once it bounces and update database.
Postfix allows piping incoming email to a particular address to a
script. So if we pipe all incoming emails to bounce@yordomain.com to
our script then we can parse the incoming address and update database.
For this, we have to edit /etc/aliases (or /etc/postfix/aliases)file as follows:
bounced: "|/path/to/your/script"
This means all incoming emails to bounced@yourdomain.com will be
piped to our script. This actually means that the whole email with
body, headers, attachments etc is forwarded to our script.
The /etc/aliases file is a text file that is used by postfix as a
table to redirect mail for local recipients. To rebuild this table
after a change, we need to run newaliases command
This will rebuild the table for postfix. Now we have completed the
second part of the process.
The shell script will get the bounced email content now. There can be
multiple bounced emails generated at the same time. So we can’t
directly pass them to rails runner scripts or rake tasks. Because that
will kill our server by launching multiple rails instances. Instead we
need to use some background tasks mechanism.
We were already using resque, so decided to use it for bounced emails
also. So a resque worker will actually update the database. Our script
just has to enqueue the job for resque.
We broke this enqueuing process into two parts.
First - A shell script which will use correct RVM Ruby version and
call the ruby script.
Second - A Ruby script which will enqueue the job to resque.
So the shell script looked like -
#!/bin/bash
rvm use ruby_version@ruby_gemset
ruby /path/to/ruby/script
And Ruby script looked like
require 'rubygems'
require 'resque'
# Adds the incoming bounced_email to background job
class BouncedEmail
def initialize(content)
Resque.enqueue_to(:bounced_email_receiver, 'BouncedEmailReceiver', content)
end
BouncedEmail.new($stdin.read)
We had to go in 2 steps here because we had multiple apps using multiple
rubies on same server. If you have only one ruby then you can make a
executable ruby script instead of shell script which decides which
ruby to use.
Now its upto resque worker to parse the content and update database.
For that, we used bounced_email gem which
detects lot of things such as bounced code, reason, type of failure
etc. As it is integrated with mail gem, we got the recipient
address(which was unique pattern generated by us only) and were able
to parse it to update the database. With bounced_email we got some
more relevant information for free :)
References :
- http://keakaj.com/wisdom/2007/08/08/verp-on-rails/
- http://blog.sosedoff.com/2011/08/10/processing-emails-with-postfix-and-rails/
- https://github.com/mitio/bounce_email
18 Jan 2014
I was trying to append some part of the DOM to some other element of
the page.
<div id='container'>
<ul class='contacts_list'>
</ul>
</div>
...
<div id='updated_contacts'>
</div>
On a click event, i wanted to append contacts_list to
updated_contacts. Using jQuery and append method
$("#updated_contacts").append($(".contacts_list"));
But every time, the original contacts_list from container was
getting removed.
After searching documentation of
append method, i found out that when an element is inserted to some
other part of DOM, it is removed from the original location.
If an element selected this way is inserted into a single location
elsewhere in the DOM, it will be moved into the target (not cloned):
Using clone method we can solve this problem.
clone creates a copy of the existing element and appends it to new
location keeping original version as it is.
$("#updated_contacts").append($(".contacts_list").clone());
Documentation of clone method is here
Using clone() has the side-effect of producing elements with
duplicate id attributes, which are supposed to be unique.
Where possible, it is recommended to avoid cloning elements with this
attribute or using class attributes as identifiers instead.
is important point to consider while using clone.
Update :
Prashant pointed out that the clone
and append methods are part of native javascript itself. And jQuery
makes use of them to build simpler API.
Javascript has appendChild and cloneNode methods which can be used
when we are not using jQuery in same situation.
More info about these methods can be found here.
Thanks Prashant :)
21 Dec 2013
If you have skipped minitest/test-unit while creating a rails app with -T or
want to move to minitest from rspec or want to start with minitest in
an existing rails project without tests, its very easy.
Just include
require "rails/test_unit/railtie"
in config/application.rb.
After this rake test will start working. You may have to create test
folder structure on your own or can copy from an existing project with tests.
26 Oct 2013
I have a very complex query which is made up of more than 1
subqueries. Arel is awesome, but it can’t generate that query. So i
generate those subqueries separately and combine them by union or
intersection based on some condition. Finally the generated query is
given to find_by_sql to get the data.
We found out that, in the jbuilder template that was rendering this
data, that it was calling association objects resulting in n+1 query
problem.
Generally this problem is solved by eager-loading in rails.
For eg. to load the company of the user, we do
@users = User.where(status: 'connected').includes(:company)
Rails will do the magic(load the company of the user also in the same query) and when we refer to @user.company from
view, it would not trigger any new sql query and directly access it
from ruby object.
But this doesn’t work with find_by_sql.
@users = User.find_by_sql(some_condition).includes(:company)
will throw error. Because find_by_sql returns Ruby array and not
ActiveRecord::Relation object. So it doesn’t respond to includes.
If we try calling includes first,
@users = User.includes(:company).find_by_sql(some_conditions)
The includes part is silently dropped and only find_by_sql part
gets executed.
ActiveRecord::Associations::Preloader class to our rescue.
Only applicable for Rails 3 and Rails 4.0.x
We can use the run method from Preloader class like follows:
@users = User.find_by_sql(some_condition)
ActiveRecord::Associations::Preloader.new(@users, :company).run
This will preload the company association for the @users object like
it will do when we use includes.
Rails 4.1 and onwards
Rails 4.1 onwards, run method is not present in Preloader class.
It is replaced by the preload method which was private in Rails 3. We can call
preload method directly as follows.
@users = User.find_by_sql(some_condition)
ActiveRecord::Associations::Preloader.new.preload(@users, :company)
The first argument to this method is records array, second argument is
associations and third is options which are optional.
We can pass a single association like :company.
We can also pass multiple associations in the form of array [:company, :account].
We can also pass a hash to eager load associations of associations
like { company: :category }.
We can also mix last two options like [{ company: :category }, :account].
Rails 5?
Things can change. The Preloader class might be replaced by a module. I will
update the blog post once that is done.
Happy Hacking!
26 Oct 2013
I had a requirement of adding facebook integration with our Rails app.
I am using omniauth-facebook gem for the authentication part and it
works great.
Our app has multiple subdomains for all clients, so i wanted to
callback URLs separate for each client.
For example,
For foo.example.com, callback should be http://foo.example.com/auth/facebook
For bar.example.com, callback should be http://bar.example.com/auth/facebook
We can do that in our Facebook app settings, using App Domains field.
The description of App Domains is as follows:
Enable auth on domain and subdomain(s) (e.g., “example.com” will enable *.example.com)
To test this locally, i added entries in /etc/hosts/ for testing
127.0.0.1 foo.myapp.com
127.0.0.1 bar.myapp.com
127.0.0.1 baz.myapp.com
Then accessing foo.myapp.com:3000 and bar.myapp.com:3000 and
clicking on facebook authenticaton, it redirected me correctly to
foo.myapp.com:3000/auth/facebook and
bar.myapp.com:3000/auth/facebook respectively.
In production, we have to replace the App Domain with actual URL of our website.
14 Oct 2013
T.L.D.R
You can pass blank object to where clause and it will return
current relation as it is.
Long version
Sometimes, we need to apply where clause conditionally.
For eg. apply timeframe condition if timeframe is given in params.
We can achieve this using simple if/unless.
def most_recent(from = nil, to = Date.today)
condition = Activity.where("created_at < ?", to)
condition.where("created_at > ?", from) unless from.blank?
end
This works but doesn’t look good. If we can chain this second
conditional scope, it would be much better.
Enter magic of Rails. If we read documentation of where clause,
# === blank condition
#
# If the condition is any blank-ish object, then #where is a no-op and returns
# the current relation.
This is interesting. This means if we pass any blank value to where
clause, it returns the current relation as it is.
Now we have to just write a method which will generate the query if
condition is satisfied. It will return nil otherwise resulting in a
no-op.
def most_recent(from = nil, to = Date.today)
Activity.where("created_at < ?", to).where(from_condition(from))
end
def from_condition(from)
"created_at > #{from}" unless from.blank?
end
This looks more cleaner than earlier solution. It will work the same
way if we pass '', "", {}, [], false or any other object
that respond to blank as true instead of nil.
Happy Hacking!