error_or 0.0.7 error_or: ^0.0.7 copied to clipboard
Return a result ErrorOr with either a value T or an error Object.
ErrorOr #
Return a result ErrorOr
with either a value T
or an error Object
.
Features #
Always return a valid value ErrorOr
from an async function. Let the called /
inner function handle the error and return an ErrorOr
. This way the caller /
outer function can await
the result without a try catch
.
A subclass of ErrorOr
contains either the expected value T
or an error
Object
(usually an Exception
returned from a try catch
).
Internally, we create a private subclass of ErrorOr
, either a _ValueWrapper
or an _ErrorWrapper
, with the expected non-null value.
ErrorOr
can be used for non-async functions too - for both Flutter and Dart.
Getting started #
Make a function return a Future<ErrorOr>
, which you'll await
in the calling
function.
Create a ErrorOr
instance by calling one of its factory constructors value
or error
.
Check hasError
or hasValue
, before calling error
or value
. If either is
called without the proper check, a TypeError
is thrown.
Usage #
Example
Future<ErrorOr<LocationPermission>> checkPermission() async {
try {
return ErrorOr.value(await Geolocator.checkPermission());
} catch (e) {
return ErrorOr.error(e);
}
}
ErrorOr<LocationPermission> errorOrPermission = await checkPermission();
if (errorOrPermission.hasError) {
return errorOrPermission;
}
LocationPermission permission = errorOrPermission.value;
Additional information #
I would like to keep this package minimal, but please get in touch on github if you have suggestions to improvements.
The name was inspired by the ErrorOr
type of SerenityOS.
The Success / Failure pattern was inspired by result_type.