Rails JSON Serialization of Decimal adds Quotes

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The only “safe” way to hand decimals from language A to language B is to use a String. If your json contains "rating": 98.79999999999999 it will probably be converted to 98.79999999999998 by your JavaScript runtime.

See BigDecimal as_json documentation:

A BigDecimal would be naturally
represented as a JSON number. Most
libraries, however, parse non-integer
JSON numbers directly as floats.
Clients using those libraries would
get in general a wrong number and no
way to recover other than manually
inspecting the string with the JSON
code itself.

That’s why a JSON string is returned.
The JSON literal is not numeric, but
if the other end knows by contract
that the data is supposed to be a
BigDecimal, it still has the chance to
post-process the string and get the
real value.

If you want to force Rails not to quote these, you could monkey-patch BigDecimal (see Rails source).

# not needed: to compare with the Numeric implementation
class Numeric
  def as_json(options = nil) self end #:nodoc:
  def encode_json(encoder) to_s end #:nodoc:
end

class BigDecimal
  def as_json(options = nil) self end
  def encode_json(encoder) to_s end #:nodoc:
end

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