YAML_TAG | = | 'tag:yaml.org,2002:float' |
YAML_MAPPING | = | { 'Infinity' => '.Inf', '-Infinity' => '-.Inf', 'NaN' => '.NaN' } |
DEFAULT_STRING_FORMAT | = | 'F' |
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.
[ show source ]
# File activesupport/lib/active_support/json/encoding.rb, line 177 177: def as_json(options = nil) to_s end
[ show source ]
# File activesupport/lib/active_support/core_ext/big_decimal/conversions.rb, line 22 22: def to_formatted_s(format = DEFAULT_STRING_FORMAT) 23: _original_to_s(format) 24: end
This emits the number without any scientific notation. This is better than self.to_f.to_s since it doesn’t lose precision.
Note that reconstituting YAML floats to native floats may lose precision.
[ show source ]
# File activesupport/lib/active_support/core_ext/big_decimal/conversions.rb, line 14 14: def to_yaml(opts = {}) 15: YAML.quick_emit(nil, opts) do |out| 16: string = to_s 17: out.scalar(YAML_TAG, YAML_MAPPING[string] || string, :plain) 18: end 19: end