Returns the string value of the environment declaration name
.
Environment declarations are provided by the surrounding system compiling or running the Dart program. Declarations map a string key to a string value.
If name
is not declared in the environment, the result is instead defaultValue
.
Example of getting a value:
const String.fromEnvironment("defaultFloo", defaultValue: "no floo")
Example of checking whether a declaration is there at all:
var isDeclared = const String.fromEnvironment("maybeDeclared") != null;
// 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 String.fromEnvironment(String name, {String defaultValue});
© 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/String/String.fromEnvironment.html