result_monad 2.3.2
result_monad: ^2.3.2 copied to clipboard
A Dart implementation of the Result Monad which allows for more expressive result generation and processing without using exceptions.
A Dart implementation of the Result Monad found in Rust and other languages. This models either success (ok) or failure (error) of operations to allow for more expressive result generation and processing without using exceptions.
This blog post I wrote goes into the backgrounds of Result Monads and steps through the various aspects of the implementation for this library.
Features #
- Result Monad with standard
ok
anderror
constructors - Methods/properties for directly querying if it is encapsulating a success or failure result and to get those values
runCatching
andrunCatchingAsync
to encapsulate thrown exception objects into error ResultsgetValueOrElse
andgetErrorOrElse
methods to return a default value if it is not the respective desired monadandThen
,transform
,andThenAsync
,transformAsync
for chaining together operations with short-circuit capabilitywithResult
andwithResultAsync
for processing results in a pass-through capability with short-circuiting on thrown exceptionswithError
andwithErrorAsync
for processing errors in a pass-through capability with short-circuiting on thrown exceptionsmapValue
,mapError
,errorCast
methods for transforming success and failure typesmatch
method for performing different operations on a success or failure monadfold
method for transforming the monad into a new result type with different logic for
Getting started #
In the pubspec.yaml
of your Dart/Flutter project, add the following dependency:
dependencies:
result_monad: ^2.3.2
In your source code add the following import:
import 'package:result_monad/result_monad.dart';
Usage #
Below is a simple example but see the repository for feature rich versions:
import 'package:result_monad/result_monad.dart';
Result<double, String> invert(double value) {
if (value == 0) {
return Result.error('Cannot invert zero');
}
return Result.ok(1.0 / value);
}
void main() {
// Prints 'Inverse is: 0.5'
invert(2).match(
onSuccess: (value) => print("Inverse is: $value"),
onError: (error) => print(error));
// Prints 'Cannot invert zero'
invert(0).match(
onSuccess: (value) => print("Inverse is: $value"),
onError: (error) => print(error));
}
Additional information #
This result monad implementation takes inspiration from the Rust result type and the Kotlin Result implementation of the Result Monad.
The pub.dev package page can be found here.