Re: Newbie questions on the meanings of things in Ruby

On Mon, Jul 16, 2012 at 9:04 AM, Alex S. <[e-mail]> wrote:
> Hi,
>
> I am tasked with the development of puppet provider. I am a few days
> into Ruby and looking at the existing providers I am finding it hard to
> interpret - I went over Ruby pargprog book and I am still not sure what
> the following syntax means. I was hoping someone might be kind enough to
> guide me through the terms here. This is the code  fragment I am
> struggling to understand:
>
> Puppet::Type.type(:file).provide :posix do
>   desc "Uses POSIX functionality to manage file ownership and
> permissions."
>
>   confine :feature => :posix
>
>   include Puppet::Util::POSIX
>   include Puppet::Util::Warnings
>
>   require 'etc'
>
>   def uid2name(id)
>     return id.to_s if id.is_a?(Symbol) or id.is_a?(String)
>     return nil if id > Puppet[:maximum_uid].to_i
>
>     begin
>       user = Etc.getpwuid(id)
>     rescue TypeError, ArgumentError
>       return nil
>     end
>
>     if user.uid == ""
>       return nil
>     else
>       return user.name
>     end
>   end
>
> ....
>
> end
>
> In particular I am finding it hard to understand what the first line
> means -
>
> Puppet::Type.type(:file).provide :posix do
>
> ?
>
> Is this some sort of dynamic class (Type) extension? If so is there a
> resource I can go to dig up a bit more on this?

I've never used Puppet, so I can only comment on the syntax part:

Puppet::Type is a constant, which looks like it refers to a class or module.
You are calling the method #type of that class or module, passing the
parameter :file (which is a symbol).
In order to read more documentation about this method, you can ri
Puppet::Type#type or look into Puppet's documentation.
This method returns an object, on which you call the method #provide,
passing the argument :posix and a block. A block is what is contained
between the do...end syntax, so basically the rest of the snippet is
the block you pass.

Without knowing anything about Puppet, it seems that this piece of
code creates a new class or an extension for Puppet's file type, in
order to provide this uid2name method.

Hope this helps,

Jesus.