34.復合模式 · 我愛 Ruby

## 34.復合模式看看下面的代碼 [iling_egg.rb](code/design_patterns/boiling_egg.rb) 。輸入并執行 ```rb ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 ```rb | ``` require_relative "node.rb" class BuyEggs < Node attr_accessor :time_in_minutes def initialize @time_in_minutes = 15 super "Buy eggs" end end class BoilEggs < Node attr_accessor :time_in_minutes def initialize @time_in_minutes = 10 super "Boil eggs" end end class PeelEggs < Node attr_accessor :time_in_minutes def initialize @time_in_minutes = 3 super "Peel eggs" end end class ServeEggs < Node attr_accessor :time_in_minutes def initialize @time_in_minutes = 2 super "Serve eggs" end end class BoiledEggs < Node def initialize super "Boiled eggs" add_child BuyEggs.new add_child BoilEggs.new add_child PeelEggs.new add_child ServeEggs.new end def total_time_in_minutes total = 0 for child in self.children total += child.time_in_minutes end total end end boiled_eggs = BoiledEggs.new puts "Time (in minutes) to make boiled eggs is #{boiled_eggs.total_time_in_minutes}." ```rb | ``` 輸出量 ```rb Time (in minutes) to make boiled eggs is 30. ``` 在復合模式中，我們將一個類分為許多類。假設需要以面向對象的方式表示煮雞蛋，我們可以將`BoiledEggs`編寫為如下所示的類。 ```rb class BoiledEggs < Node def initialize super "Boiled eggs" add_child BuyEggs.new add_child BoilEggs.new add_child PeelEggs.new add_child ServeEggs.new end def total_time_in_minutes total = 0 for child in self.children total += child.time_in_minutes end total end end ``` `BoiledEggs`繼承了一個名為`Node`的類，該類有助于構建樹結構。稍后再討論`Node`類。現在讓我們專注于復合模式。如你在`initialize`方法中所見，在該類中`BoiledEggs`被劃分為許多類，即`BuyEggs`至`ServeEggs`，并且它們被作為子節點添加到`BoiledEggs`中。如果你可以看到類`BuyEggs`如下所示： ```rb class BuyEggs < Node attr_accessor :time_in_minutes def initialize @time_in_minutes = 15 super "Buy eggs" end end ``` 如果看到類`ServeEggs`，則如下所示： ```rb class ServeEggs < Node attr_accessor :time_in_minutes def initialize @time_in_minutes = 2 super "Serve eggs" end end ``` 實際上，它看起來與`BuyEggs`非常相似，因此可以按照相似的方式處理這些類。因此`BoiledEggs`就像是由不同對象組成的，可以用相似的方式對其進行處理。現在`BoiledEggs`中的每個類都具有`time_in_minutes`屬性。因此，如果我們需要以分鐘為單位計算制作煮雞蛋的總時間，我們要做的就是編寫一個函數`total_time_in_minutes`，如下所示 ```rb class BoiledEggs < Node ... def total_time_in_minutes total = 0 for child in self.children total += child.time_in_minutes end total end end ``` 因此，復合模式可以用于存在復雜對象的地方，可以將其功能分解為較小的對象，可以以非常相似的方式處理這些較小的對象，并將這些較小的對象放置在樹狀結構中。談論樹結構，我們建立了一個名為`Node`的類，可以在文件 [node.rb](code/design_patterns/node.rb) 中找到該類。你可以在下面看到它。 ```rb ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 ```rb | ``` class Node attr_accessor :name, :parent, :children def initialize name = "node" @name = name @parent = nil @children = [] end def to_s "<Node: #{@name}, id: #{self.object_id}>" end def add_child node children << node node.parent = self end end ```rb | ``` 它具有一個稱為`add_child`的功能，通過它我們可以添加子元素。你可以使用`parent`功能獲取節點的父節點。要查看此節點類的工作方式，請看下面的代碼 [Composite.rb](code/design_patterns/composite.rb) ： ```rb ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 ```rb | ``` # composite.rb require_relative "node.rb" n1 = Node.new "n1" n2 = Node.new "n2" n3 = Node.new "n3" n1.add_child n2 n1.add_child n3 puts "children of #{n1} are:" for node in n1.children puts node end puts puts "Parent of #{n3} is #{n3.parent}" ```rb | ``` Output ```rb children of <Node: n1, id: 47253445808700> are: <Node: n2, id: 47253445808560> <Node: n3, id: 47253445808360> Parent of <Node: n3, id: 47253445808360> is <Node: n1, id: 47253445808700> ```