如何在 Ruby 中声明一个二维数组
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How to declare a two-dimensional array in Ruby
提问by kadrian
I want a twodimensional array in Ruby, that I can access for example like this:
我想要一个 Ruby 中的二维数组，我可以像这样访问它：
if @array[x][y] == "1" then @array[x][y] = "0"
The problem is: I don't know the initial sizes of the array dimensions and i grow the array (with the <<operator).
问题是：我不知道数组维度的初始大小，我增加了数组（使用<<运算符）。
How do I declare it as an instance variable, so I get no error like this?
如何将其声明为实例变量，以免出现此类错误？
undefined method `[]' for nil:NilClass (NoMethodError)
QUESTION UPDATED:
问题更新：
@array = Array.new {Array.new}
now works for me, so the comment from Matt below is correct!
现在对我有用，所以下面马特的评论是正确的！
I just found out the reason why I received the error was because I iterated over the array like this:
我刚刚发现我收到错误的原因是因为我像这样迭代了数组：
for i in [email protected]
for j in 0..@array[0].length
@array[i][j] ...
which was obviously wrong and produced the error. It has to be like this:
这显然是错误的并产生了错误。它必须是这样的：
for i in [email protected]
for j in 0..@array[0].length-1
@array[i][j] ...
采纳答案by csherin
A simple implementation for a sparse 2-dimensional array using nested Hashes,
使用嵌套哈希的稀疏二维数组的简单实现，
class SparseArray
attr_reader :hash
def initialize
@hash = {}
end
def [](key)
hash[key] ||= {}
end
def rows
hash.length
end
alias_method :length, :rows
end
Usage:
用法：
sparse_array = SparseArray.new
sparse_array[1][2] = 3
sparse_array[1][2] #=> 3
p sparse_array.hash
#=> {1=>{2=>3}}
#
# dimensions
#
sparse_array.length #=> 1
sparse_array.rows #=> 1
sparse_array[0].length #=> 0
sparse_array[1].length #=> 1
回答by Marc Talbot
Matt's comment on your question is totally correct. However, based on the fact that you've tagged this "conways-game-of-life", it looks like you are trying to initialize a two dimensional array and then use this in calculations for the game. If you wanted to do this in Ruby, one way to do this would be:
马特对你的问题的评论是完全正确的。但是，基于您已经标记了这个“conways-game-of-life”这一事实，您似乎正在尝试初始化一个二维数组，然后在游戏的计算中使用它。如果您想在 Ruby 中执行此操作，一种方法是：
a = Array.new(my_x_size) { |i| Array.new(my_y_size) { |i| 0 }}
which will create a my_x_size * my_y_size array filled with zeros.
这将创建一个 my_x_size * my_y_size 填充零的数组。
What this code does is to create a new Array of your x size, then initialize each element of that array to be another Array of your y size, and initialize each element of each second array with 0's.
这段代码的作用是创建一个 x 大小的新数组，然后将该数组的每个元素初始化为另一个 y 大小的数组，并用 0 初始化每个第二个数组的每个元素。
回答by Marc-André Lafortune
Ruby's Arraydoesn't give you this functionality.
RubyArray没有给你这个功能。
Either you manually do it:
要么您手动执行此操作：
(@array[x] ||= [])[y] = 42
Or you use hashes:
或者你使用哈希：
@hash = Hash.new{|h, k| h[k] = []}
@hash[42][3] = 42
@hash # => {42 => [nil, nil, nil, 42]}
