Rails 1.2 introduced native Decimal-support in ActiveRecord. This enabled us to use decimal-columns in migrations without the need to drop back to SQL. Also the Decimal-columns are now returned as BigDecimal-objects by ActiveRecord. During the migration from 1.1 to 1.2, the tests of two applications suddenly showed the follwing problem:

TypeError: BigDecimal can't be coerced into BigDecimal

The problem was caused by the serialization of a data-structure including BigDecimals because YAML currently can't store BigDecimals.

A short search on the web showed other people with the same problem and some good advice and also a ticket but no solution which transparently loads the BigDecimal-objects back from the YAML-file.

The source of the problem is that BigDecimal has no YAML-representation and so is YAMLed with the standard approach of a generic object. But a YAML line like "--- !ruby/object:BigDecimal {}" doesn't help a lot when reconstructing the number.

So I want to share my workaround:



I just open BigDecimal and redefine the output of to_yaml with a custom type and the string-representation of the BigDecimal. As I am not sure what the type of BigDecimal will be in the official version I just used a tag including my domain name. For me it's not a big deal, as I am using YAML just for caching. If you use YAML for persistent storage, be aware of a potentially conflicting official solution at some point in the future.

For the Rails-people out there I have packaged it up in a small plugin.

(As usual, use everything at your own risk!)