From: Farrel Lifson <farrel.lifson@...>
Date: 2009-11-18T08:17:15+09:00
Subject: object.to_yaml works but [ object ].to_yaml fails

I've implemented a custom to_yaml method for an object. When I call
to_yaml on the object everything works as expected.

rb(main):008:0> puts area.to_yaml
---
Area Description: Deltana, Tanana Flats
Polygons: []
Geocodes:
  UGC: AKZ223
  FIPS6: 002290
Circles: []

Ceiling:
Altitude:
=> nil

However when I put the object in an array I get the following error

irb(main):009:0> puts [ area ].to_yaml
TypeError: wrong argument type String (expected Data)
        from /usr/lib/ruby/1.8/yaml.rb:391:in `emit'
        from /usr/lib/ruby/1.8/yaml.rb:391:in `quick_emit'
        from /usr/lib/ruby/1.8/yaml/rubytypes.rb:107:in `to_yaml'
        from (irb):9

Here is the implementation of Area#to_yaml

def to_yaml( options = {} )
       {
         AREA_DESC_YAML => self.area_desc,
         ALTITUDE_YAML  => self.altitude,
         CEILING_YAML   => self.ceiling,
         CIRCLES_YAML   => self.circles,
         GEOCODES_YAML  => self.geocodes.inject({}){|h,geocode|
h.merge( geocode.name => geocode.value )},
         POLYGONS_YAML  => self.polygons
       }.to_yaml
end

AREA_DESC_YAML and the others are just strings like "Area Description"
etc. I'm not enough of a YAML expert to understand why serialization
fails when the area object is in an array.

Farrel
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