From: why the lucky stiff <ruby-talk@...>
Date: 2004-05-26T16:15:44+09:00
Subject: Re: 3 yaml questions...

Martin Pirker wrote:
> Hi.... I need help :-/

Hello, Martin and his slanty jaw.

> --- !seq
> - "Path: ...!not-for-mail\nFrom: ...
> - "Path: ...!not-for-mail\nFrom: ...
> - "Path: ...!not-for-mail\nFrom: ...
> - |
>   Path: ...!not-for-mail
>   From: ...
>   Subject: ...
> [...]
> - "Path: ...!not-for-mail\nFrom: ...
> - "Path: ...!not-for-mail\nFrom: ...
> [...]
> 
> Question: Why are some articles one liners with \n while others are
> dumped in original linebreak style?

The String#to_yaml method uses a routine to find a good fit for whatever 
  string you're passing in.  It might be because there are some 
non-printables or some whitespace that needs to be preserved.

In the last few weeks I've recoded alot of that logic.  I think it is 
becoming superior.  (Try Ruby CVS.)

If you want to force certain objects to be block literals (indicated by 
the pipe character), you can create `to_yaml_fold' methods for those 
objects.  Either do it in the class definition or in the singleton.

   o = "Here's one in a singleton"
   def o.to_yaml_fold; '|'; end
   puts o.to_yaml

   outputs:
   --- |
   Here's one in a singleton

This sort of technique is only available in the latest snapshots.  But 
it will be prevalent by Ruby 1.8.2.

> 
> seq: [ a, b, c ]
> 
> Question: So far I was unable to dump the short style from Ruby - how 
> to...?
> 

The emitter isn't equipped to dump inline arrays currently.  Shortly it 
will be available similiar to what you see above.

   o = ['a', 'b', 'c']
   def o.to_yaml_format; :inline; end

I haven't decided completely on this, though.  So, we'll see.

> 
> 3) yaml+bzip2
> 
> The yaml ascii dumps may get large, any easy way to auto filter 
> load/save through bzip2?
> 

Sure.  All the YAML loading/parsing methods accept IO objects.  If the 
file has a bz2 suffix, use the BZ2::Reader.

   reader = if filename =~ /\.bz2$/
              BZ2::Reader
            else
              File
            end
   obj = reader.open( filename ) do |f|
           YAML::load( f )
         end

YAML::dump can write to IO.

   writer = if filename =~ /\.bz2$/
              BZ2::Writer
            else
              File
            end
   writer.open( filename, 'w' ) do |f|
     YAML::dump( obj, f )
   end


_why