Array.Add与+ = [英] Array.Add vs +=

问题描述

我在PowerShell数组中发现了一些有趣的行为，也就是说，如果我将数组声明为:

I've found some interesting behaviour in PowerShell Arrays, namely, if I declare an array as:

$array = @()

然后尝试使用$array.Add("item")方法向其中添加项目，我收到以下错误:

And then try to add items to it using the $array.Add("item") method, I receive the following error:

使用"1"作为参数调用添加"的异常:集合的大小固定."

Exception calling "Add" with "1" argument(s): "Collection was of a fixed size."

但是，如果我使用$array += "item"附加商品，则该商品可以毫无问题地被接受，并且固定尺寸"限制似乎并不适用.

However, if I append items using $array += "item", the item is accepted without a problem and the "fixed size" restriction doesn't seem to apply.

这是为什么?

推荐答案

使用$array.Add()方法时，您试图将元素添加到现有数组中.数组是固定大小的集合，因此您将收到一个错误消息，因为它无法扩展.

When using the $array.Add()-method, you're trying to add the element into the existing array. An array is a collection of fixed size, so you will receive an error because it can't be extended.

$array += $element创建一个 new 数组，该数组具有与旧元素相同的元素+新项目，而这个新的较大数组替换了$array-变量

$array += $element creates a new array with the same elements as old one + the new item, and this new larger array replaces the old one in the $array-variable

您可以使用+ =运算符将元素添加到数组.当你 使用 Windows PowerShell实际上使用它的值创建了一个新数组. 原始数组和附加值.例如，添加带有 值$ 200到$ a变量中的数组，键入:

You can use the += operator to add an element to an array. When you use it, Windows PowerShell actually creates a new array with the values of the original array and the added value. For example, to add an element with a value of 200 to the array in the $a variable, type:

    $a += 200

来源: about_Arrays

+=是一项昂贵的操作，因此当您需要添加许多项目时，应尝试以尽可能少的操作添加它们，例如:

+= is an expensive operation, so when you need to add many items you should try to add them in as few operations as possible, ex:

$arr = 1..3    #Array
$arr += (4..5) #Combine with another array in a single write-operation

$arr.Count
5

如果这不可能，请考虑使用更有效的集合，例如List或ArrayList(请参阅其他答案).

If that's not possible, consider using a more efficient collection like List or ArrayList (see the other answer).

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