| // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| part of dart.core; |
| |
| /** |
| * The reserved words [:true:] and [:false:] denote objects that are the only |
| * instances of this class. |
| * |
| * It is a compile-time error for a class to attempt to extend or implement |
| * bool. |
| */ |
| class bool { |
| /** |
| * Returns the boolean value of the environment declaration [name]. |
| * |
| * The boolean value of the declaration is `true` if the declared value is |
| * the string `"true"`, and `false` if the value is `"false"`. |
| * |
| * In all other cases, including when there is no declaration for `name`, |
| * the result is the [defaultValue]. |
| * |
| * The result is the same as would be returned by: |
| * |
| * (const String.fromEnvironment(name) == "true") |
| * ? true |
| * : (const String.fromEnvironment(name) == "false") |
| * ? false |
| * : defaultValue |
| * |
| * Example: |
| * |
| * const loggingFlag = const bool.fromEnvironment("logging"); |
| * |
| * If you want to use a different truth-string than `"true"`, you can use the |
| * [String.fromEnvironment] constructor directly: |
| * |
| * const isLoggingOn = (const String.fromEnvironment("logging") == "on"); |
| */ |
| external const factory bool.fromEnvironment(String name, |
| {bool defaultValue: false}); |
| |
| /** |
| * Returns [:"true":] if the receiver is [:true:], or [:"false":] if the |
| * receiver is [:false:]. |
| */ |
| String toString() { |
| return this ? "true" : "false"; |
| } |
| } |