Dart折叠vs减少 [英] Dart Fold vs Reduce

问题描述

Dart中的折叠和缩小之间有什么区别？我应该何时使用一个而不是另一个？他们似乎根据文档做同样的事情。

What's the difference between fold and reduce in Dart and when would I use one as opposed to the other? They seem to do the same thing according to the docs.

通过迭代地组合每个
元素，将集合减少为单个值

Reduces a collection to a single value by iteratively combining each element of the collection with an existing value using the provided function.

推荐答案

fold 可用于所有情况。

例如，您无法计算列表中所有字符串的长度之和与 reduce 。您必须使用 fold ：

For instance you cannot compute the sum of the length of all strings in a list with reduce. You have to use fold :

final list = ['a', 'bb', 'ccc'];
// compute the sum of all length
list.fold(0, (t, e) => t + e.length); // result is 6

顺便说一下 list.reduce（f） / code>可以看作是 list.skip（1）.fold（list.first，f）的快捷方式。

By the way list.reduce(f) can be seen as a shortcut for list.skip(1).fold(list.first, f).

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