[Capistrano] Re: Local Variable Problems

[Jamis Buck]

You need to make sure you are setting tier via -S. If you aren't, then the tier variable won't be set.

  unless variables.include?(:tier)
    set :tier, "sandbox"
  end

- Jamis

On Nov 2, 2006, at 10:44 AM, V. Orion Delwaterman wrote:

If you want to test for whether a variable has been set or not, you can do:

Hi Jamis,

Yes this does explain alot.  I tried the command that you recommended:

if tier.nil?
     set :tier, "sandbox"
end



Orion Delwaterman


deals with local variables. What you want is to use set(), instead of
assignment, since variables in capistrano are not really Ruby
variables. Try this:

   if tier.nil?
     set :tier, "sandbox"
   end

That should do the trick. Now, if you're curious about the behavior
you saw, read on:

First, a simple example. Suppose you have the following Ruby script:

   p x

If you execute that command, you'll get an exception, "undefined
local variable or method `x'". However, if you do something like this:

   if false
     x = "hello"
   end

   p x

You'll now get the output 'nil'. Even though x is never explicitly
set! This is because Ruby will silently vivify x, due to its
reference in the body of the if.

Now, Capistrano handles variables specially. It actually keeps a hash
of key/value pairs, and uses method_missing to hook into that. Thus,
your capistrano script can say:

  p tier

and have it just work, even though you do not explicitly set tier as
a local variable. So, let's look at your example:

   p tier #-> gives 'dev'

   if tier.nil?  #-> this is false
     tier = 'sandbox'
   end

   p tier #-> gives 'null'

The first line works in capistrano, not because tier is a local
variable, but because of method_missing. The local variable is not
actually defined, so method_missing gets called, which looks up the
variable and returns the value.

Ditto for the condition in the if clause.

However, you are setting a local variable in the body of the if,
which causes ruby to implicitly vivify 'tier' as a local variable,
with a value of nil. The next time you ask for 'tier', that local
variable is used, and method_missing does not get called.

Hope that makes sense,

Jamis

On Nov 2, 2006, at 9:12 AM, [EMAIL PROTECTED] wrote:

>
> I am trying to write my deploy script that will work for multiple
> deployment environments (sandbox, dev, staging, production).  While
> working on this I ran into a problem with variable assignment.  I
> wrote
> some debug scripts to check on somethings and got the strangest
> results.  Here is what I wrote in my deploy.rb:
>
> puts "tier: #{tier}" if !tier.nil?
> puts tier.nil?.to_s
> puts "tier: #{tier}" if !tier.nil?
> puts tier.nil?.to_s
> if tier.nil?
>   tier = 'sandbox'
> end
> puts "tier: #{tier}"
> #puts "ENV[]: " + ENV["TIER"] if !ENV["TIER"]
> raise "stop"
>
> I then run the following command from my command line:
> cap -S tier=dev deploy
>
> This is what is outputted to my console:

> deploy
>     loading configuration
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capis
> trano-1.2.0/lib/capistrano/recipes/standard.rb
>     loading configuration ./config/deploy.rb
>     loading configuration
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/mongr
> el_cluster-0.2.0/lib/mongrel_cluster/recipes.rb
> tier: dev
> false
> tier: dev
> false
> tier:
> ./config/deploy.rb:35:in `load': stop (RuntimeError)
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/l
> ib/capistrano/configuration.rb:146:in `load'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/l
> ib/capistrano/configuration.rb:125:in `load'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0 /l
> ib/capistrano/configuration.rb:125:in `load'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/l
> ib/capistrano/cli.rb:252:in `execute_recipes!'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/l
> ib/capistrano/cli.rb:252:in `execute_recipes!'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano- 1.2.0/l
> ib/capistrano/cli.rb:233:in `execute!'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/l
> ib/capistrano/cli.rb:12:in `execute!'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/b
> in/cap:11
>         from C:/Ruby/InstantRails/ruby/bin/cap:18
>
> As you can see on the last line before the exception is thrown the
> variable tier suddenly goes to nil.  If I then comment out the
> following line:
>
> if tier.nil?
> #  tier = 'sandbox'
> end
>
> I get the following output:
>

> deploy
>     loading configuration
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capis
> trano-1.2.0/lib/capistrano/recipes/standard.rb
>     loading configuration ./config/deploy.rb
>     loading configuration
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/mongr
> el_cluster-0.2.0/lib/mongrel_cluster/recipes.rb
> tier: dev
> false
> tier: dev
> false
> tier: dev
> ./config/deploy.rb:35:in `load': stop (RuntimeError)
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/l
> ib/capistrano/configuration.rb:146:in `load'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/l
> ib/capistrano/configuration.rb:125:in `load'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0 /l
> ib/capistrano/configuration.rb:125:in `load'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/l
> ib/capistrano/cli.rb:252:in `execute_recipes!'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/l
> ib/capistrano/cli.rb:252:in `execute_recipes!'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano- 1.2.0/l
> ib/capistrano/cli.rb:233:in `execute!'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/l
> ib/capistrano/cli.rb:12:in `execute!'
>         from
> C:/Ruby/InstantRails/ruby/lib/ruby/gems/1.8/gems/capistrano-1.2.0/b
> in/cap:11
>         from C:/Ruby/InstantRails/ruby/bin/cap:18
>
> The problem has disappeared.  It seems like capistrano is doing
> something weird for an assignment to a local variable that it should
> not even be executing.  Please Help!?!?!?
>
>
> [EMAIL PROTECTED]
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But I got an exception that states that the variable "tier" does not exsist in the Capistrano:Configuration Object. To get around the problem I am using ENV variables right now. But would much rather use the command line. Any ideas? On 11/2/06, Jamis Buck <[EMAIL PROTECTED]> wrote: Ah, this is a subtle one. You're running into an aspect of how Ruby > C:\Ruby\InstantRails\rails_apps\video_content_manager>cap -S tier=dev > C:\Ruby\InstantRails\rails_apps\video_content_manager>cap -S tier=dev To unsubscribe from this group, send email to capistrano- [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/ group/capistrano

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