使用 `Array.new(n, Array.new)` 创建矩阵 [英] Creating matrix with `Array.new(n, Array.new)`
问题描述
我通过执行以下操作创建了一个数组:
I created an array by doing the following:
@gameboard = Array.new(3, Array.new(3, " "))
我试图分配一个这样的值,我得到了这个:
I tried to assign a value like so, and I got this:
@gameboard[0][2] = "X"
@gameboard #=> [[" ", " ", "X"], [" ", " ", "X"], [" ", " ", "X"]]
当我以不同的方式声明数组时,
When I declare the array differently,
@gameboard = [[" ", " ", " "], [" ", " ", " "], [" ", " ", " "]]
我得到了这个结果:
@gameboard[0][2] = "X"
@gameboard # => [[" ", " ", "X"], [" ", " ", " "], [" ", " ", " "]]
为什么在为数组赋值时使用 Array.new
方法会导致不同的行为?
Why does using the Array.new
method illicit different behavior when assigning values to the array?
推荐答案
关注代码:
@gameboard = Array.new(3, Array.new(3, " "))
@gameboard.map { |a| a.object_id }
# => [76584030, 76584030, 76584030]
表示 new(size=0, obj=nil)
方法创建一个size
的数组,具有相同的ob
.
means new(size=0, obj=nil)
method creates an array of size
, having the same ob
.
但是 new(size){|索引|块 }
方法以不同的方式工作;它创建了一个 size
的数组,具有不同的 obs
.
But new(size) {|index| block }
method works in a different way; it creates an array of size
, having different obs
.
查看下面的代码:
@gameboard = Array.new(3) { Array.new(3, " ") }
@gameboard.map { |a| a.object_id }
# => [75510080, 75509920, 75509540]
以上与您的第二个代码示例相同:
The above is the same as your second code example:
@gameboard = [[" ", " ", " "], [" ", " ", " "], [" ", " ", " "]]
@gameboard.map { |a| a.object_id }
# => [80194090, 80193400, 80193080]
如果更改或更新@gameboard
的第一个元素数组的索引1
处的值,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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