ActiveSupport::Deprecation::DeprecatedConstantProxy

DeprecatedConstantProxy transforms a constant into a deprecated one. It takes the full names of an old (deprecated) constant and of a new constant (both in string form) and a deprecator. The deprecated constant now returns the value of the new one.

PLANETS = %w(mercury venus earth mars jupiter saturn uranus neptune pluto)

# (In a later update, the original implementation of `PLANETS` has been removed.)

PLANETS_POST_2006 = %w(mercury venus earth mars jupiter saturn uranus neptune)
PLANETS = ActiveSupport::Deprecation::DeprecatedConstantProxy.new("PLANETS", "PLANETS_POST_2006", ActiveSupport::Deprecation.new)

PLANETS.map { |planet| planet.capitalize }
# => DEPRECATION WARNING: PLANETS is deprecated! Use PLANETS_POST_2006 instead.
     (Backtrace information…)
     ["Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"]