From: why the lucky stiff <ruby-talk@...>
Date: 2005-05-12T09:07:17+09:00
Subject: Re: defining a custom to_yaml method to inline hashes

Ara.T.Howard@noaa.gov (Ara.T.Howard@noaa.gov) wrote:
> On Wed, 11 May 2005, Ara.T.Howard wrote:
> > # attempt to bludgeon to object into emitting in an inline fashion
> > class << inline_hash
> >   def to_yaml(*a, &b)
> >     '{ ' << map{|kv| kv.join(': ')}.join(', ') << ' }'
> >   end
> > end

Hacking Syck 0.45 or less will be very involved.  Consider that inline
collections must also contain inline hashes and inline arrays.  And, as
your sample code demonstrated, some strings which get formatted in the
"folded" or "literal" block styles won't jive with inlines.

Syck 0.53 and up is a different story.  You can easily emit inlines by
defining a `to_yaml_style' method.

  >> require 'yaml'
  >> a = {'time' => Time.now, 'jid' => 121, 'metric' => 'started'}
  >> def a.to_yaml_style; :inline; end
  >> y a
  => ---
     { time: 2005-05-10 08:18:22.523016, jid: 121, metric: started }

The new Syck emitter will ensure that everything inside the inline is
properly output.  I still need to improve the pretty printer, but it
works.

> this seems o.k. - can anyone verify this is an o.k. approach?
> 
>   jib:~ > cat a.rb
>   require 'yaml'
>   class Hash
>     def yaml_inline= bool
>       unless defined? @__yaml_inline_meth
>         @__yaml_inline_meth =
>           lambda {|opts|
>             YAML::quick_emit(id, opts) {|emitter|
>               emitter << '{ ' << map{|kv| kv.join ': '}.join(', ') << ' }'
>             }
>           }
>         class << self
>           def to_yaml opts = {}
>             @__yaml_inline ? @__yaml_inline_meth[ opts ] : super
>           end
>         end
>       end
>       @__yaml_inline = bool
>     end
>   end

This will work for very simple hashes, but will break down upon
encountering multiline strings or any kind of object, array, hash, etc.

While Syck 0.5x isn't ready for primetime, it's getting very close.  I
could use help debugging and the time you spend debugging could yield a
stable Syck in the next two months.

_why