• 一个 dart app 是一个 library
• library 是隐私单元

使用库

• 内建库: dart:
• 文件系统路径
• 包管理器: package:

import 'dart:html';
import 'package:test/test.dart';

指定库前缀

import 'package:lib1/lib1.dart';
import 'package:lib2/lib2.dart' as lib2;
// Uses Element from lib1.
Element element1 = Element();
// Uses Element from lib2.
lib2.Element element2 = lib2.Element();

导入部分库

// Import only foo.
import 'package:lib1/lib1.dart' show foo;
// Import all names EXCEPT foo.
import 'package:lib2/lib2.dart' hide foo;

惰加载库

• web app 用
• deferred as

import 'package:greetings/hello.dart' deferred as hello;
// 手动加载
Future greet() async {
  await hello.loadLibrary();
  hello.printGreeting();
}

实现库