Ruby-on-rails – What’s a Capfile? And how to use it correctly with Ruby on Rails

capistranorubyruby-on-rails

I have a ruby on rails application that should be transferred from one server to another (that's not working fine at the moment). I installed capistrano. I'm using debian 7 server with apache passenger.

I saw a Capfile in the root directory of the ruby on rails application.
Is a Capfile something like a makefile to build and deploy the application? How do I correctly work with it?

UPDATE

When I run the cap file i got this: ' cap deploy:setup '

(Backtrace restricted to imported tasks)
cap aborted!
LoadError: cannot load such file -- config/deploy
/var/www/myapplication/Capfile:3:in `load'
/var/www/myapplication/Capfile:3:in `<top (required)>'
(See full trace by running task with --trace)

it seems like the deploy file coun't be loaded … i have in the config folder an deploy folder and a deploy.rb

whats going wrong?

Best Answer

This is happening because Capistrano tasks are now Rake tasks and Rake expects a construct like this:

task :name, [:arg, :arg] => :dependency do
  ...
end

Capistrano 3:

task :dump do
  on primary roles :db do
    ...
  end
end

Related Solutions

Ruby-on-rails – How to understand nil vs. empty vs. blank in Ruby

.nil? can be used on any object and is true if the object is nil.

.empty? can be used on strings, arrays and hashes and returns true if:

String length == 0
Array length == 0
Hash length == 0

Running .empty? on something that is nil will throw a NoMethodError.

That is where .blank? comes in. It is implemented by Rails and will operate on any object as well as work like .empty? on strings, arrays and hashes.

nil.blank? == true
false.blank? == true
[].blank? == true
{}.blank? == true
"".blank? == true
5.blank? == false
0.blank? == false

.blank? also evaluates true on strings which are non-empty but contain only whitespace:

"  ".blank? == true
"  ".empty? == false

Rails also provides .present?, which returns the negation of .blank?.

Array gotcha: blank? will return false even if all elements of an array are blank. To determine blankness in this case, use all? with blank?, for example:

[ nil, '' ].blank? == false
[ nil, '' ].all? &:blank? == true

Ruby – How to write a switch statement in Ruby

Ruby uses the case expression instead.

case x
when 1..5
  "It's between 1 and 5"
when 6
  "It's 6"
when "foo", "bar"
  "It's either foo or bar"
when String
  "You passed a string"
else
  "You gave me #{x} -- I have no idea what to do with that."
end

Ruby compares the object in the when clause with the object in the case clause using the === operator. For example, 1..5 === x, and not x === 1..5.

This allows for sophisticated when clauses as seen above. Ranges, classes and all sorts of things can be tested for rather than just equality.

Unlike switch statements in many other languages, Ruby’s case does not have fall-through, so there is no need to end each when with a break. You can also specify multiple matches in a single when clause like when "foo", "bar".

Best Answer

Related Solutions

Ruby-on-rails – How to understand nil vs. empty vs. blank in Ruby

Ruby – How to write a switch statement in Ruby

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