avoid_slow_async_io.md

Pattern: Use of slow async dart:io method

Issue: -

Description

AVOID using the following asynchronous file I/O methods because they are much slower than their synchronous counterparts.

• Directory.exists
• Directory.stat
• File.lastModified
• File.exists
• File.stat
• FileSystemEntity.isDirectory
• FileSystemEntity.isFile
• FileSystemEntity.isLink
• FileSystemEntity.type

Example of incorrect code:

import 'dart:io';

Future<Null> someFunction() async {
 var file = new File('/path/to/my/file');
 var now = new DateTime.now();
 if ((await file.lastModified()).isBefore(now)) print('before'); // LINT
}

Example of correct code:

import 'dart:io';

Future<Null> someFunction() async {
 var file = new File('/path/to/my/file');
 var now = new DateTime.now();
 if (file.lastModifiedSync().isBefore(now)) print('before'); // OK
}

Further Reading

• Linter for Dart - avoid_slow_async_io