函数`runZoned`的'dart:async'的目的

Question

runZoned提供的特殊功能dart:async.该文件在此处:https://api.dartlang.org/docs/channels/stable/latest/dart_async.html#runZoned

我不确定这个功能的目的是什么,我们什么时候需要它,以及如何正确使用它？

Answer 1

看看这段代码:

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");
}

产量

Unhandled exception:
I am bad

现在看看这段代码:

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");
}

产量

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

badMethod如果可能的话,你应该严格避免使用.

只有在不可能的情况下,您才可以临时使用 runZoned

您也可以使用runZoned模拟sandboxed任务的执行.