数组行为异常 [英] Arrays misbehaving

问题描述

代码如下:

# a = Array.new(3, Array.new(3))
a = [[nil,nil,nil],[nil,nil,nil]]
a[0][0] = 1
a.each {|line| p line}

输出:

[1, nil, nil]
[nil, nil, nil]

但使用注释行:

[1, nil, nil]
[1, nil, nil]
[1, nil, nil]

那是为什么?

推荐答案

注释行将三个相同引用分配给数组，因此对一个数组的更改将传播到其他引用到它.

The commented line is assigning three of the same reference to the array, so a change to one array will propagate across the other references to it.

对于 2 个数组与 3 个数组，这只是第一行指定 3 作为其第一个参数并仅在第二行中指定 2 个数组文字的问题.

As for the 2 arrays vs 3, that's simply a matter of the first line specifying 3 as its first parameter and only specifying 2 array literals in the second line.

在没有任何共享引用的情况下创建嵌套数组:

To create the nested arrays without having any shared references:

a = Array.new(3) {Array.new(3)}

当传入一个块({...} 或 do ... end)时，Array.new 会调用这个块来获取每个元素的值数组.

When passed a block ({...} or do ... end), Array.new will call the block to obtain the value of each element of the array.

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