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# encoding: UTF-8
module TZInfo
# A proxy class standing in for a {Timezone} with a given identifier.
# {TimezoneProxy} inherits from {Timezone} and can be treated identically to
# {Timezone} instances loaded with {Timezone.get}.
#
# {TimezoneProxy} instances are used to avoid the performance overhead of
# loading time zone data into memory, for example, by {Timezone.all}.
#
# The first time an attempt is made to access the data for the time zone, the
# real {Timezone} will be loaded is loaded. If the proxy's identifier was not
# valid, then an exception will be raised at this point.
class TimezoneProxy < Timezone
# Initializes a new {TimezoneProxy}.
#
# The `identifier` parameter is not checked when initializing the proxy. It
# will be validated when the real {Timezone} instance is loaded.
#
# @param identifier [String] an IANA Time Zone Database time zone
# identifier.
def initialize(identifier)
super()
@identifier = identifier
@real_timezone = nil
end
# (see Timezone#identifier)
def identifier
@real_timezone ? @real_timezone.identifier : @identifier
end
# (see Timezone#period_for)
def period_for(time)
real_timezone.period_for_utc(time)
end
# (see Timezone#periods_for_local)
def periods_for_local(local_time)
real_timezone.periods_for_local(local_time)
end
# (see Timezone#transitions_up_to)
def transitions_up_to(to, from = nil)
real_timezone.transitions_up_to(to, from)
end
# (see Timezone#canonical_zone)
def canonical_zone
real_timezone.canonical_zone
end
# Returns a serialized representation of this {TimezoneProxy}. This method
# is called when using `Marshal.dump` with an instance of {TimezoneProxy}.
#
# @param limit [Integer] the maximum depth to dump - ignored. @return
# [String] a serialized representation of this {TimezoneProxy}.
# @return [String] a serialized representation of this {TimezoneProxy}.
def _dump(limit)
identifier
end
# Loads a {TimezoneProxy} from the serialized representation returned by
# {_dump}. This is method is called when using `Marshal.load` or
# `Marshal.restore` to restore a serialized {Timezone}.
#
# @param data [String] a serialized representation of a {TimezoneProxy}.
# @return [TimezoneProxy] the result of converting `data` back into a
# {TimezoneProxy}.
def self._load(data)
TimezoneProxy.new(data)
end
private
# Returns the real {Timezone} instance being proxied.
#
# The real {Timezone} is loaded using {Timezone.get} on the first access.
#
# @return [Timezone] the real {Timezone} instance being proxied.
def real_timezone
# Thread-safety: It is possible that the value of @real_timezone may be
# calculated multiple times in concurrently executing threads. It is not
# worth the overhead of locking to ensure that @real_timezone is only
# calculated once.
unless @real_timezone
result = Timezone.get(@identifier)
return result if frozen?
@real_timezone = result
end
@real_timezone
end
end
end
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