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FluentResults is a lightweight Dart library developed to solve a common problem. It returns an object indicating success or failure of an operation instead of throwing/using exceptions.

fluent_result #

pub package codecov likes style: lint Dart

fluent_result is a lightweight Dart library developed to solve a common problem. It returns an object indicating success or failure of an operation instead of throwing/using exceptions.

  • Store multiple errors in one Result object
  • Store powerful and elaborative Error object instead of only error messages in string format
  • Designing Errors in an object-oriented way

Usage #

Creating a Result #

Create a result which indicates success

Result result = Result.success();
Result successResult1 = Result.ok; // equivalent to a `Result.success()` but shorter

Create a result which indicates failure

Result errorResult1 = Result.withErrorMessage('a fail reason');
Result errorResult2 = Result.withError(ResultError('my error message'));
Result errorResult3 = Result.withException(MyException('exception description'));

Generic ResultOf<T> #

Success result with value:

ResultOf<MyObject> result = ResultOf.success(MyObject());
MyObject value = result.value;

Fail result with error and without value:

ResultOf<MyObject> result = ResultOf.fail<MyObject>(ResultError('a fail reason'));
MyObject value = result.value; // is null because of the fail result

failIf() and okIf() #

With the methods failIf() and okIf() you can also write in a more readable way:

final result1 = Result.failIf(() => firstName.isEmpty, "First Name is empty");
final result2 = Result.okIf(() => firstName.isNotEmpty, 'First name should not be empty');

Converting Result to another #

To convert one success result to another success result has to be provided a valueConverter

final anotherResult =
    result.toResult(valueConverter: (customer) => User(customer.id));

To convert one fail result to another fail result

final anotherResult = failResult.toResult<Customer>();

Custom errors #

To make your codebase more robust. Create your own error collection of the App by extending ResultError.
ResultError has key property which you can use for localization.


class InvalidPasswordError extends ResultError {
  const InvalidPasswordError(String message)
      : super(message, key: 'InvalidPasswordError');
}

class CustomerNotFound extends ResultError {
  const CustomerNotFound({
    required this.customerId,
  }) : super('Customer not found with ID $customerId');

  final int customerId;

  @override
  String toString() => message;
}

Collect errors #

For example, easy to work with errors which comes from HTTP API.

final err1 = CustomerNotFound(customerId: 1);
final res = Result.fail(err1);

final err2 = InvalidPasswordError('The password 123456 is invalid');
res.add(err2);

res.contains<InvalidPasswordError>(); // true
res.get<InvalidPasswordError>().should.not.beNull();

Contributing #

We accept the following contributions:

  • Improving documentation
  • Reporting issues
  • Fixing bugs

Maintainers #

15
likes
110
pub points
84%
popularity

Publisher

verified publisherdevcraft.ninja

FluentResults is a lightweight Dart library developed to solve a common problem. It returns an object indicating success or failure of an operation instead of throwing/using exceptions.

Repository (GitHub)
View/report issues

Documentation

API reference

License

MIT (LICENSE)

Dependencies

collection, quiver

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