ruby - 如何更改 ruby 二维数组中的一个单元格？

Question

谁能解释一下？

def digit_block(size = 1)
  col = 2 + 1*size
  row = 1 + 2*size
  r = []
  for i in 0...col
    r.push ' '
  end
  a = []
  for i in 0...row
    a.push r
  end
  a
end

block = digit_block
puts block.inspect
block[1][2] = 'x'
puts block.inspect

输出:

[[" ", " ", " "], [" ", " ", " "], [" ", " ", " "]]
[[" ", " ", "x"], [" ", " ", "x"], [" ", " ", "x"]]

我的理解是 block[1][2] 只改变了第 1 行第 2 列的单元格，但为什么它改变了第 2 列的所有单元格？

Answer 1

  for i in 0...row
    # you are pushing the same array object to an array
    a.push r
  end

所以 block 中的每个元素都是同一个对象。

block[0] === block[1]  # true
block[1] === block[2]  # true

更新:

您需要为每个元素创建一个新数组，您的代码可以重写如下:

def digit_block(size = 1)
  Array.new(1 + 2*size){Array.new(2 + size){' '}}
end