Groovy中的注入方法是什么? [英] What is Inject Method in Groovy?

问题描述

Groovy中的 inject 方法实际上是做什么的?我用谷歌搜索，但没有找到确切的答案.任何人都可以通过一个简单的示例来指定其用途吗?

What does the inject method in Groovy actually do? I googled it, and have not found the exact answer. Can anyone specify its use with a simple example?

推荐答案

它将操作应用于集合并跟踪中间值.举个例子: [1、2、3、4] .inject(0，{sum，value-> sum + value}).也就是说，将0用作初始值，然后将加法运算应用于中间结果和每个元素.该操作的每次应用都会产生一个新的中间结果.在这种情况下，闭包将数字相加，因此将生成列表的总和.您可以像这样想象它:

It applies an operation to a collection and keeps track of an intermediate value. Take this example: [1, 2, 3, 4].inject(0, { sum, value -> sum + value }). This says use 0 as the initial value and apply the addition operation to the intermediate result and each element in sequence. Each application of the operation generates a new intermediate result. In this case, the closure adds up the numbers, so it generates the sum of the list. You can imagine it like:

<initial value> <operation> <element1> <operation> ... <elementn>

或者，对于 [1、2、3、4] .inject(0，{sum，value-> sum + value}):

0 + 1 + 2 + 3 + 4

要查找列表的乘积，可以使用 [1、2、3、4] .inject(1，{乘积，值->乘积*值}).在这种情况下，将1用作初始值，因为它是多重复制的标识值.

To find the product of a list, you can use [1, 2, 3, 4].inject(1, { product, value -> product * value}). In this case, 1 is used as the initial value, since it is the identity value for mulitplication.

这是一个将多单词字符串列表拆分为平面单词列表的示例:

Here's an example that splits a list of multi-word strings into a flat list of words:

strings = ["", "this", "is a", "test of inject!"]
words = strings.inject([], { list, value -> list + value.tokenize() })
assert words == ["this", "is", "a", "test", "of", "inject!"]

有时用于描述此操作的其他术语是"reduce"，如 MapReduce 或折叠"(具体是折叠).

Other terms that are sometimes used to describe this operation are "reduce", as in MapReduce, or a "fold" (specifically a foldl).

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