description

# String.fromEnvironment constructor Null safety

const String.fromEnvironment(

1. String name,
2. {String defaultValue: ""}

)

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")

In order to check whether a declaration is there at all, use bool.hasEnvironment. Example:

    const maybeDeclared = bool.hasEnvironment("maybeDeclared")
        ? String.fromEnvironment("maybeDeclared")
        : null;

## Implementation

    // 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 = ""});