数组排序的Ruby中的数组 [英] Sorting an array of arrays in Ruby

问题描述

我有数组像这样的数组：

I have an array of arrays like so:

irb(main):028:0> device_array
=> [["name1", "type1", ["A", "N", "N"], ["Attribute", "device_attribute"], 9], ["name2","type2", ["A", "N", "N"], ["Attribute", "device_attribute"], 7]]

我想，第4单元对整个device_array排序。

I would like to sort the entire device_array on the 4th element.

我试过

AllDevicesController.all_devices.sort do | a,b |
  for i in 0..(AllDevicesController.all_devices.length - 1) do
    a[i][4] <=> b[i][4]
  end
end

我也试过：

AllDevicesController.all_devices.sort do | a,b |
  a[][4] <=> b[][4]
end

这两种方法都没有奏效。

Both methods have not worked.

我是用这个作为参考：
<一href=\"http://ariejan.net/2007/01/28/ruby-sort-an-array-of-objects-by-an-attribute/\">http://ariejan.net/2007/01/28/ruby-sort-an-array-of-objects-by-an-attribute/

我想我失去了一些东西rubyish使这很容易。

I imagine I'm missing something rubyish that makes this really easy.

推荐答案

您不能使用＆LT; =＆GT; 与无。

您code应该是这样的：

Your code should be something like this:

AllDevicesController.all_devices.sort do |a, b|
  a[4].nil? ? -1 : b[4].nil? ? 1 : a[4] <=> b[4]
end

这将使子阵，在结果的开始没有索引4的元素。要做到这一点的其他方式，交换 1 与 1 。

This will put the sub-arrays that have no element of index 4 at the beginning of the result. To do it the other way around, swap -1 with 1.

您也可以使用 sort_by 而不是排序。我觉得这已经用Ruby 1.8.7（所以如果你使用的是旧版本，它可能无法正常工作）被引入。它会是这样的：

You could also use sort_by instead of sort. I think this has been introduced in Ruby 1.8.7 (so it might not work if you are using an older version). It goes something like:

AllDevicesController.all_devices.sort_by { |e| e.nil? ? 0 : e[4] }

这会把子阵，无4元，如果它是0更改此常量适合你。

This will treat sub-arrays with no 4th element as if it was 0. Change this constant to suit you.

编辑：

在你调整的投入，现在很清楚你是非常接近正确的答案。您code应该是：

After you adjusted the input, it is now clear you were very close to the right answer. Your code should have been:

AllDevicesController.all_devices.sort do |a, b|
  a[4] <=> b[4]
end

或简单的（假设的Ruby 1.8.7或以上）：

Or simple (assuming Ruby 1.8.7 or more):

AllDevicesController.all_devices.sort_by { |e| e[4] }

在这两种情况下，变量 A 和 B 将包含原始数组中的元素，这就是为什么你可以直接在任意位置访问一个元素（你不需要像 A [] [4] ，这是不正确的Ruby语法）。

In both cases, the variables a and b will contain elements of the original array, this is why you can directly access an element in any position (and you don't need something like a[][4], which is incorrect Ruby syntax).

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