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Contents
require "delegate"
module ShopifyCli
##
# `LazyDelegator` defers initialization of its underlying delegatee until the
# latter is accessed for the first time due to a method call that the
# delegator cannot handle itself:
#
# result = LazyDelegator.new do
# # carry out costly operation ...
# end
#
# result # referencing the object itself does not result in Proc evaluation
# result.to_h # however, calling a method on it will result in Proc evaluation
#
# LazyDelegator lends itself to being subclassed in scenarios where some
# facts are known and others are costly to compute:
#
# class LazySpecificationHandler < ShopifyCli::LazyDelegator
# attr_reader :identifier
#
# def initialize(identifier, &initializer)
# super(&initializer)
# @identifier = identifier
# end
# end
#
# handler = LazySpecificationHandler.new(:product_subscription) do
# # fetch specification from the Partners Dashboard API ...
# end
#
# # Accessing identifier will not result in Proc evaluation as it is
# # available as an attribute of the delegator itself
# handler.identifier # => :product_subscription
#
# # Accessing the specification will result in evaluation of the Proc
# # and in our example in a subsequent network call
# handler.specification # => <Extension::Models::Specifcation:...>
#
class LazyDelegator < SimpleDelegator
def initialize(&delegatee_initializer)
super([false, delegatee_initializer])
end
protected
def __getobj__(*)
initialized, value_or_initializer = super
return value_or_initializer if initialized
value_or_initializer.call.tap do |value|
__setobj__([true, value])
end
end
end
end
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20 entries across 20 versions & 1 rubygems