Registry Generator

If you want a Rails initializer seeded with common type registrations, generate one:

bin/rails generate amounts:registry fiat
bin/rails generate amounts:registry metals
bin/rails generate amounts:registry crypto
bin/rails generate amounts:registry all

That writes config/initializers/amounts.rb with curated Amount.register calls.

What each preset contains

• fiat: a basket of major fiat currencies with appropriate display symbols and UI decimals
• metals: precious and industrial metals, including display units for troy-ounce and kilogram-style presentation
• crypto: a basket of major crypto assets and stablecoins, including unit helpers such as satoshis, gwei, and lamports where useful
• all: the union of the three presets with duplicate symbols removed

What the generator does not do

It does not register default rates.

That is intentional because rates are directional and application-specific:

Amount.register_default_rate :USD, :USDC, "1"
Amount.register_default_rate :USDC, :USD, "1"

Add only the pairs your application actually means.