如何定Array＃新的工作块形式＆QUOT; Array.new（10）{| E | E = E * 2}＆QUOT;？ [英] How does the block form of Array#new work given "Array.new(10) { |e| e = e * 2 }"?

问题描述

我无法理解花括号内的部分。

I am having trouble understanding the part inside the curly braces.

Array.new(10) { |e| e = e * 2 }
# => [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]   

我得到与十个值的新数组被创建，但什么是下半年做什么？

I get that a new array with ten values is created, but what is the second half doing?

推荐答案

让我们在这个具体为：

nums = Array.new(10)

这将创建10个元素的新数组。对于每个数组元素。它经过指定的控制块：

This creates a new array with 10 elements. For each array element it passes control to the block specified by:

{ |e| e = e * 2 }

的 | E | 重新presents元素的索引。该指数是阵列中的位置。这从0开始，因为数组有10个元素在9结束。第二部分乘以2的索引和返回值。这是因为 E * 2 ，是该块中的最后一条语句，则返回。 返回，然后应用到该元素的值的值因此，我们最终用下面的数组：

The |e| represents the element's index. The index is the position in the array. This starts at 0 and ends at 9 since the array has 10 elements. The second part multiplies the index by 2 and returns the value. This is because the e * 2, being the last statement in the block, is returned. The value returned is then applied to that element's value. So we end up with the following array:

[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]

修改

正如PJS，避免在路上，问题写在同一code更简单的方式提到的是：

As mentioned by pjs and to avoid problems down the road, a simpler way to write the same code would be:

Array.new(10) { |e| e * 2 }

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