Question

我是ruby的首发，我真的坚持使用这段代码......我无法理解为什么@plays会在调用test_code时发生变化

class Board
  attr_reader :plays

  def initialize(secret_code)  
    @secret_code = secret_code
    @plays = []               
  end

  def insert_code(code)  
    @plays.push(code)          
    p @plays         #-> [["red", "red", "red", "red"]]
    test_code(code)  #-> When i call this method the changes on 'code' make to '@plays' array...
    p @plays         #-> [["check", "red", "red", "red"]]
  end

  private

  def test_code(code)
    s_code = @secret_code  # made a copy of @secret_code to keep it intact but is changing just like @plays
    s_code.each_index do |i|
      if s_code[i] == code[i]
        s_code[i] = "O"
        code[i] = "check"  #in this line the @plays array is changed, and i can't figure out why
      end
    end
  end
end

board = Board.new(["red", "blue", "blue", "blue"])
board.insert_code(["red", "red", "red", "red"])

Answer 1

赋值运算符=不会复制对象。它为对象创建一个新的引用（即指针）。

您可以使用clone创建对象的浅表副本，如下所示：

...
s_code = @secret_code.clone
...
def test_code(code0)
  code = code0.clone
...

Answer 2

你像这样定义了@plays：

  def insert_code(code)  
    @plays.push(code)          # here is not a clone but a quote
  end

运行methond＆＃34; test_code＆＃34;后，变量＆＃34; code＆＃34>更改为[＆＃34;检查＆＃34;，＆＃34;红色＆＃34;，＆＃34;红色＆＃34;，＆＃34;红色＆＃34;] 所以你看@plays也改为[[＆＃34; check＆＃34;，＆＃34; red＆＃34;，＆＃34; red＆＃34;，＆＃34; red＆＃34;]] < / p>

为什么我的实例变量会间接改变？

2 个答案: