dart - `runZoned`的功能 'dart:async'的目的

runZoned提供了一个特殊的功能dart:async。该文件在这里:https://api.dartlang.org/docs/channels/stable/latest/dart_async.html#runZoned

我不确定此功能的目的是什么，我们什么时候需要它，以及如何正确使用它？

最佳答案

看下面的代码:

import 'dart:async';

void main() {
  fineMethod().catchError((s) {}, test : (e) => e is String);
  badMethod().catchError((s) {}, test : (e) => e is String);
}

Future fineMethod() {
  return new Future(() => throw "I am fine");
}

Future badMethod() {
  new Future(() => throw "I am bad");
  return new Future(() => throw "I am fine");
}

输出

Unhandled exception:
I am bad

现在看下面的代码:

import 'dart:async';

void main() {
  fineMethod().catchError((s) {}, test : (e) => e is String);

  runZoned(() {
    badMethod().catchError((s) {}, test : (e) => e is String);
  }, onError : (s) {
    print("It's not so bad but good in this also not so big.");
    print("Problem still exists: $s");
  });
}

Future fineMethod() {
  return new Future(() => throw "I am fine");
}

Future badMethod() {
  new Future(() => throw "I am bad");
  return new Future(() => throw "I am fine");
}

输出

It's not so bad but good in this also not so big.
Problem still exists: I am bad

如果可能，您应严格避免使用badMethod。

只有在这种情况下，您才可以临时使用runZoned
您也可以使用runZoned模拟任务的sandboxed执行。