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");
// The .fromEnvironment() constructors are special in that we do not want // users to call them using "new". We prohibit that by giving them bodies // that throw, even though const constructors are not allowed to have bodies. // Disable those static errors. //ignore: const_constructor_with_body //ignore: const_factory external const factory bool.fromEnvironment(String name, {bool defaultValue: false});
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/2.0.0/dart-core/bool/bool.fromEnvironment.html