simply_result 1.0.0

A lightweight Result type for Dart with functional helpers, async support, and zero dependencies.

simply_result

A lightweight Result type for Dart.

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Features

• Functional Result type
• Success / Error modeling
• Functional helpers (map, flatMap, zip)
• Async helpers
• Zero dependencies
• High test coverage

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API Index

Quick dictionary of all helpers available in simply_result.

• simply_result
  • Features
  • API Index
  • Installation
  • API
  • success(value)
  • error(err)
  • map
  • flatMap
  • mapError
  • fold
  • getOrElse
  • zip
  • zip3
  • mapAsync
  • flatMapAsync
  • pipe
  • Res.unit()

Installation

dependencies:
  simply_result: ^1.0.0

API

success(value)

Creates a successful result containing a value.

Use it when an operation completes correctly.

final result = success(10);

print(result);
// → Success(10)

---

error(err)

Creates a failed result containing an error.

Useful for returning failures without throwing exceptions.

final result = error("network failure");

print(result);
// → Error(network failure)

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map

Transforms the value only if the result is Success. If the result is Error, it is propagated unchanged.

final result = success(5)
    .map((v) => v * 2);

print(result);
// → Success(10)

Error propagation:

final result = error("fail")
    .map((v) => v * 2);

print(result);
// → Error(fail)

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flatMap

Chains operations that also return a Res.

Useful for composing multiple fallible operations.

final result = success(5)
    .flatMap((v) => success(v * 2));

print(result);
// → Success(10)

Error propagation:

final result = error("fail")
    .flatMap((v) => success(v * 2));

print(result);
// → Error(fail)

---

mapError

Transforms the error value without touching the success value.

final result = error("network")
    .mapError((e) => "Error: $e");

print(result);
// → Error(Error: network)

---

fold

Handles both success and error cases, returning a single value.

final result = success(10).fold(
  (err) => "Error: $err",
  (value) => "Value: $value",
);

print(result);
// → Value: 10

With error:

final result = error("fail").fold(
  (err) => "Error: $err",
  (value) => "Value: $value",
);

print(result);
// → Error: fail

---

getOrElse

Returns the value if success, otherwise returns a fallback.

final value = success(10)
    .getOrElse(() => 0);

print(value);
// → 10

With error:

final value = error("fail")
    .getOrElse(() => 0);

print(value);
// → 0

---

zip

Combines two results into one.

If any result is Error, the first error is returned.

final result = Res.zip(
  success(2),
  success(3),
  (a, b) => a + b,
);

print(result);
// → Success(5)

With error:

final result = Res.zip(
  success(2),
  error("fail"),
  (a, b) => a + b,
);

print(result);
// → Error(fail)

---

zip3

Combines three results.

final result = Res.zip3(
  success(2),
  success(3),
  success(5),
  (a, b, c) => a + b + c,
);

print(result);
// → Success(10)

---

mapAsync

Asynchronous version of map.

final result = await success(5)
    .mapAsync((v) async => v * 2);

print(result);
// → Success(10)

---

flatMapAsync

Asynchronous version of flatMap.

final result = await success(5)
    .flatMapAsync((v) async => success(v * 2));

print(result);
// → Success(10)

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pipe

Allows chaining transformations in a functional pipeline style.

final result = success(5)
    .pipe((r) => r.map((v) => v * 2));

print(result);
// → Success(10)

---

Res.unit()

Creates a success result containing null. Useful when the operation has no meaningful return value.

final result = Res.unit();

print(result);
// → Success(null)