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# frozen_string_literal: true
module Valkyrie
##
# ValueMapper is a way to handle coordinating extendable casting of values
# depending on what the value is. It's used in many of the adapters in
# Valkyrie.
#
# Typically a root node is defined as a sub-class ValueMapper to separate
# value mappers for a distinct purpose, but it's not a requirement.
#
# @example Defining a ValueMapper which converts symbols to strings.
# class ParentMapper < ValueMapper
# end
# class Stringify < ValueMapper
# ParentMapper.register(self)
# def self.handles?(value)
# value.kind_of?(Symbol)
# end
# def result
# value.to_s
# end
# end
# @example Use a ValueMapper
# ParentMapper.for(:symbol).result # => "symbol"
class ValueMapper
# Register a value caster.
# @param value_caster [Valkyrie::ValueMapper]
def self.register(value_caster)
self.value_casters += [value_caster]
end
# @return [Array<Valkyrie::ValueMapper>] Registered value casters.
def self.value_casters
@value_casters ||= []
end
class << self
attr_writer :value_casters
end
# Find the value caster for a given value.
# @param value [Anything] The value to find a caster for.
def self.for(value)
(value_casters + [self]).find do |value_caster|
value_caster.handles?(value)
end.new(value, self)
end
# Test whether this caster handles a given value.
# @param value [Anything]
# @return [Boolean]
def self.handles?(_value)
true
end
attr_reader :value, :calling_mapper
def initialize(value, calling_mapper)
@value = value
@calling_mapper = calling_mapper
end
# @return Casted value.
def result
value
end
end
end
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55 entries across 55 versions & 1 rubygems