dart:io同步与异步文件操作 [英] dart:io sync vs async file operations

问题描述

对于文件中的 dart:io :

• file.deleteSync()和 file.delete()
• file.readAsStringSync()和 file.readAsString()
• file.writeAsBytesSync(bytes)和 file.writeAsBytes(bytes)
• 还有很多很多.

在同步和异步选项之间进行选择时，应牢记哪些注意事项?我似乎回想起某个地方，如果您必须等待同步完成，则同步选项会更快(例如， await file.delete()).但是我不记得在哪里看到的或者是真的.

What are the considerations that I should keep in mind when choosing between the sync and async options? I seem to recall seeing somewhere that the sync option is faster if you have to wait for it to finish anyway (await file.delete() for example). But I can't remember where I saw that or if it is true.

此方法之间是否有区别:

Is there any difference between this method:

Future deleteFile(File file) async {
  await file.delete();
  print('deleted');
}

和此方法:

Future deleteFile(File file) async {
  file.deleteSync();
  print('deleted');
}

推荐答案

让我尝试根据对我的问题的评论来总结答案.纠正我在哪里错了.

Let me try to summarize an answer based on the comments to my question. Correct me where I'm wrong.

• 在 async 方法中运行代码不会使其在另一个线程上运行.
• Dart是单线程系统.
• 代码在事件循环上运行.
• 执行长时间运行的同步任务将阻塞系统，无论它是否处于异步方法中.
• 隔离是一个单线程.
• 如果要在另一个线程上运行任务，则需要在另一个隔离上运行它.
• 启动另一个隔离程序称为生成隔离程序.
• 在其他隔离环境上运行任务有一些选项，包括 compute 和 IsolateChannel 和编写自己的隔离通信代码.
• 对于文件IO，同步版本比异步版本要快.
• 对于繁重的文件IO，请首选异步版本，因为它们在单独的线程上工作.
• 对于轻量文件IO(例如 file.exists()?)，可以选择使用同步版本，因为它可能很快.

• Running code in an async method doesn't make it run on another thread.
• Dart is a single threaded system.
• Code gets run on an event loop.
• Performing long running synchronous tasks will block the system whether it is in an async method or not.
• An isolate is a single thread.
• If you want to run tasks on another thread then you need to run it on another isolate.
• Starting another isolate is called spawning the isolate.
• There are a few options for running tasks on another isolate including compute and IsolateChannel and writing your own isolate communication code.
• For File IO, the synchronous versions are faster than the asynchronous versions.
• For heavy File IO, prefer the asynchronous version because they work on a separate thread.
• For light File IO (like file.exists()?), using the synchronous version is an option since it is likely to be fast.

• 隔离和事件循环
• 单线程飞镖，什么?—第1部分
• 单线程飞镖，什么?—第2部分
• avoid_slow_async_io皮棉

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