Dart中的收益示例 [英] yield example in Dart

问题描述

如何在Dart中像Scala一样使用yield？
Scala中有一个示例 https：/ /alvinalexander.com/scala/scala-for-loop-yield-examples-yield-tutorial

How to use yield in Dart as a same as Scala? There is an example in Scala "https://alvinalexander.com/scala/scala-for-loop-yield-examples-yield-tutorial"

scala> val a = Array(1, 2, 3, 4, 5)
a: Array[Int] = Array(1, 2, 3, 4, 5)

scala> for (e <- a if e > 2) yield e
res1: Array[Int] = Array(3, 4, 5)

如何在飞镖上做？

void main() {
  var a = [1, 2, 3, 4, 5];

  for (var e in a) {
    if (e > 2) yield e;
  }
}

推荐答案

for（e<-a，如果e> 2）的表达式e 表达式是 表达式 在Scala中。
评估为数组。 Dart没有将其作为直接表达式，但是您可以使函数以几乎相同的方式返回可迭代对象，然后立即调用它们以创建表达式：

The for (e <- a if e > 2) yield e expression is an expression in Scala. It evaluates to an array. Dart does not have that as a direct expression, but you can make functions that return iterables in much the same way, and then call them immediately to create an expression:

var a = [1, 2, 3, 4, 5]
var res = () sync* { for (var v in a) if (v > 2) yield v; } ();

在这里，我介绍一个函数（）sync * {for（var v in a）如果（v> 2）产生v; } 并立即调用它。该函数返回 Iterable 。可迭代的元素是主体 yield 的值，在这种情况下为3、4和5。

Here I introduce a function () sync* { for (var v in a) if (v > 2) yield v; } and calls it immediately. That function returns an Iterable. The elements of that iterable are the values yield'ed by the body, in this case 3, 4 and 5.

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