Page 34 - Dart Language

Chapter 13: Libraries

Remarks

The import and library directives can help you create a modular and shareable code base. Every
Dart app is a library, even if it doesn’t use a library directive. Libraries can be distributed using
packages. See Pub Package and Asset Manager for information about pub, a package manager
included in the SDK.

Examples

Using libraries

Use import to specify how a namespace from one library is used in the scope of another library.

import 'dart:html';

The only required argument to import is a URI specifying the library. For built-in libraries, the URI
has the special dart: scheme. For other libraries, you can use a file system path or the package:
scheme. The package: scheme specifies libraries provided by a package manager such as the pub
tool. For example:

import 'dart:io';
import 'package:mylib/mylib.dart';
import 'package:utils/utils.dart';

Libraries and visibility

Unlike Java, Dart doesn’t have the keywords public, protected, and private. If an identifier starts
with an underscore _, it’s private to its library.

If you for example have class A in a separate library file (eg, other.dart), such as:

library other;

class A {
int _private = 0;

testA() {
print('int value: $_private'); // 0
_private = 5;
print('int value: $_private'); // 5
}
}

and then import it into your main app, such as:

https://riptutorial.com/ 29