Newbie questions on the meanings of things in Ruby

Ruby
1

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?

Thanks,
Alex.

2

On Mon, Jul 16, 2012 at 9:04 AM, Alex S. [email protected] wrote:

desc "Uses POSIX functionality to manage file ownership and
return id.to_s if id.is_a?(Symbol) or id.is_a?(String)
else

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.

3

I’m going to explain the sentence syntactically, not what it does:

Puppet::Type.type(:file).provide :posix do

Puppet is a module which have a class Type,
calls method type with the parameter :file(which is a symbol),
then call a method provide(the Puppet lib uses method chaining to create
a
domain specific language(DSL), google the terms if you must),
and this method provide has a parameter :posix.

The do … end is a block.

I advise you to get the basics straight before you dive into that kind
of
code.

Have a good day!

On Mon, Jul 16, 2012 at 4:14 AM, Jess Gabriel y Galn <