创建具有`Array.new（N，Array.new）矩阵` [英] Creating matrix with `Array.new(n, Array.new)`

问题描述

我通过以下操作创建一个数组：

I created an array by doing the following:

@gameboard = Array.new(3, Array.new(3, " "))

我试图分配一个值，像这样，我得到这个：

I tried to assign a value like so, and I got this:

@gameboard[0][2] = "X"
@gameboard #=> [[" ", " ", "X"], [" ", " ", "X"], [" ", " ", "X"]]

在我不同的声明数组，

@gameboard = [[" ", " ", " "], [" ", " ", " "], [" ", " ", " "]]

我得到这样的结果：

I get this result:

@gameboard[0][2] = "X"
@gameboard # => [[" ", " ", "X"], [" ", " ", " "], [" ", " ", " "]]

为什么到数组赋值时，使用 Array.new 方法非法不同的行为？

推荐答案

按照code：

@gameboard = Array.new(3, Array.new(3, " "))
@gameboard.map { |a| a.object_id }
# => [76584030, 76584030, 76584030]

新（大小= 0，则obj =无） 方法创建尺寸，具有相同的 OB的数组。

但 新（尺寸）{|首页|块} 方法以不同的方式工作;它创建数组尺寸，具有不同 OBS 。

查看code以下：

@gameboard = Array.new(3) { Array.new(3, " ") }
@gameboard.map { |a| a.object_id }
# => [75510080, 75509920, 75509540]

以上是一样的你的第二个code例如：

The above is the same as your second code example:

@gameboard = [[" ", " ", " "], [" ", " ", " "], [" ", " ", " "]]
@gameboard.map { |a| a.object_id }
# => [80194090, 80193400, 80193080]

如果您更改或 @gameboard 的第一个元素数组的索引 1 更新的价值，它不会影响所有其他内部数组元素。

If you change or update the the value at index 1 of the first element array of @gameboard, it wouldn't affect all other inner array elements.

@gameboard = Array.new(3) { Array.new(3, " ") }
@gameboard[0][1] = 2
@gameboard
# => [[" ", 2, " "], [" ", " ", " "], [" ", " ", " "]]

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