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我正在編寫POODR的第8章,將組合對象與組合。不過,我似乎無法讓這個例子的工作:Ruby中的布爾型參數錯誤
class Bicycle
attr_reader :size, :parts
def initialize(args = {})
@size = args[:size]
@parts = args[:parts]
end
def spares
parts.spares
end
end
require 'forwardable'
class Parts
extend Forwardable
def_delegators :@parts, :size, :each
include Enumerable
def initialize(parts)
@parts = parts
end
def spares
select { |part| part.needs_spare }
end
end
require 'ostruct'
module PartsFactory
def self.build(config, parts_class = Parts)
parts_class.new(
config.collect do |part_config|
create_part(part_config)
end
)
end
def self.create_part(part_config)
OpenStruct.new(
name: part_config[0],
description: part_config[1],
needs_spare: part_config.fetch(2, true)
)
end
end
當我使用road_config
:
road_config =
[['chain', '10-speed'],
['tire_size', '23'],
['tape_color', 'red']]
road_bike =
Bicycle.new(
size: 'L',
parts: PartsFactory.build(road_config)
)
p road_bike.spares.size
road_bike.spares.size
返回3.這是我的預期。然而,當我使用mountain_config
:
mountain_config =
[['chain', '10-speed'],
['tire_size', '2.1'],
['front_shock', 'Manitou', false],
['rear_shock', 'Fox']]
mountain_bike =
Bicycle.new(
size: 'L',
parts: PartsFactory.build(mountain_config)
)
p mountain_bike.spares.size
我期待看到4,不是如果我從front_shock
刪除false
它讓默認值(true
),mountain_bike.spares.size
返回4
爲什麼false
使mountain_bike.spares.size
返回3?我錯過了什麼?
哇,那真是愚蠢!非常感謝你。 – ogirginc