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Invalid<E, A> final ​

final class Invalid<E, A> extends Validated<E, A>

A Validated that represents a failure, or invalid value.

Inheritance

Object → Validated<E, A> → Invalid<E, A>

Available Extensions

Constructors ​

Invalid() ​

Invalid(E value)
Implementation
dart
Invalid(this.value);

Properties ​

hashCode no setter inherited ​

int get hashCode

The hash code for this object.

A hash code is a single integer which represents the state of the object that affects operator == comparisons.

All objects have hash codes. The default hash code implemented by Object represents only the identity of the object, the same way as the default operator == implementation only considers objects equal if they are identical (see identityHashCode).

If operator == is overridden to use the object state instead, the hash code must also be changed to represent that state, otherwise the object cannot be used in hash based data structures like the default Set and Map implementations.

Hash codes must be the same for objects that are equal to each other according to operator ==. The hash code of an object should only change if the object changes in a way that affects equality. There are no further requirements for the hash codes. They need not be consistent between executions of the same program and there are no distribution guarantees.

Objects that are not equal are allowed to have the same hash code. It is even technically allowed that all instances have the same hash code, but if clashes happen too often, it may reduce the efficiency of hash-based data structures like HashSet or HashMap.

If a subclass overrides hashCode, it should override the operator == operator as well to maintain consistency.

Inherited from Validated.

Implementation
dart
@override
int get hashCode => fold((e) => e.hashCode, (a) => a.hashCode);

isInvalid no setter inherited ​

bool get isInvalid

Returns true if this instance is a Invalid, otherwise false is returned.

Inherited from Validated.

Implementation
dart
bool get isInvalid => !isValid;

isValid no setter inherited ​

bool get isValid

Returns true if this instance is a Valid, otherwise false is returned.

Inherited from Validated.

Implementation
dart
bool get isValid => fold((_) => false, (_) => true);

runtimeType no setter inherited ​

Type get runtimeType

A representation of the runtime type of the object.

Inherited from Object.

Implementation
dart
external Type get runtimeType;

value final ​

final E value
Implementation
dart
final E value;

Methods ​

andThen() inherited ​

Validated<E, B> andThen<B>(Validated<E, B> Function(A) f)

Creates a new Validated by applying f if this is a Valid, otherwise returns the error value.

Inherited from Validated.

Implementation
dart
Validated<E, B> andThen<B>(Function1<A, Validated<E, B>> f) => fold(Validated.invalid, f);

bimap() inherited ​

Validated<EE, AA> bimap<EE, AA>(EE Function(E) fe, AA Function(A) fa)

Returns a new Validated by applying fe or fa depending on if this instance is an Invalid or Valid respectively.

Inherited from Validated.

Implementation
dart
Validated<EE, AA> bimap<EE, AA>(Function1<E, EE> fe, Function1<A, AA> fa) =>
    fold((e) => fe(e).invalid(), (a) => fa(a).valid());

ensure() inherited ​

Validated<E, A> ensure(bool Function(A) p, E Function() onFailure)

Tests if the valid value (if any) passes the given predicate p. If it fails, a new Invalid with a value of onFailure is returned, otherwise this instance is returned.

Inherited from Validated.

Implementation
dart
Validated<E, A> ensure(Function1<A, bool> p, Function0<E> onFailure) =>
    fold((a) => this, (a) => p(a) ? this : Validated.invalid(onFailure()));

ensureOr() inherited ​

Validated<E, A> ensureOr(bool Function(A) p, E Function(A) onFailure)

Tests if the valid value (if any) passes the given predicate p. If it fails, a new Invalid with a value of onFailure is returned, otherwise this instance is returned.

Inherited from Validated.

Implementation
dart
Validated<E, A> ensureOr(Function1<A, bool> p, Function1<A, E> onFailure) =>
    fold((a) => this, (a) => p(a) ? this : Validated.invalid(onFailure(a)));

exists() inherited ​

bool exists(bool Function(A) p)

Returns true if this instance has a valid value to passes the given predicate p.

Inherited from Validated.

Implementation
dart
bool exists(Function1<A, bool> p) => fold((_) => false, p);

fold() override ​

B fold<B>(B Function(E) fe, B Function(A) fa)

Returns the result of applying fe if this is an instance of Invalid, otherwise the result of applying fa to this Valid.

Implementation
dart
@override
B fold<B>(Function1<E, B> fe, Function1<A, B> fa) => fe(value);

forall() inherited ​

bool forall(bool Function(A) p)

Returns true if this instance has a valid value to passes the given predicate p.

Inherited from Validated.

Implementation
dart
bool forall(Function1<A, bool> p) => fold((_) => true, p);

foreach() inherited ​

void foreach(void Function(A) f)

Applies the given side-effet f for every valid value this instance represents.

Inherited from Validated.

Implementation
dart
void foreach(Function1<A, void> f) => fold((_) => Unit(), f);

getOrElse() inherited ​

A getOrElse(A Function() orElse)

Returns the value of this instance if it is a Valid, otherwise returns the result of evaluating orElse.

Inherited from Validated.

Implementation
dart
A getOrElse(Function0<A> orElse) => fold((_) => orElse(), identity);

leftMap() inherited ​

Validated<EE, A> leftMap<EE>(EE Function(E) f)

Returns a new validated by applying f to the value of this instance if it is an Invalid.

Inherited from Validated.

Implementation
dart
Validated<EE, A> leftMap<EE>(Function1<E, EE> f) => fold((e) => f(e).invalid(), (a) => a.valid());

map() inherited ​

Validated<E, B> map<B>(B Function(A) f)

Returns a new validated by applying f to the value of this instance if it is a Valid.

Inherited from Validated.

Implementation
dart
@override
Validated<E, B> map<B>(Function1<A, B> f) => fold((e) => e.invalid(), (a) => f(a).valid());

noSuchMethod() inherited ​

dynamic noSuchMethod(Invocation invocation)

Invoked when a nonexistent method or property is accessed.

A dynamic member invocation can attempt to call a member which doesn't exist on the receiving object. Example:

dart
dynamic object = 1;
object.add(42); // Statically allowed, run-time error

This invalid code will invoke the noSuchMethod method of the integer 1 with an Invocation representing the .add(42) call and arguments (which then throws).

Classes can override noSuchMethod to provide custom behavior for such invalid dynamic invocations.

A class with a non-default noSuchMethod invocation can also omit implementations for members of its interface. Example:

dart
class MockList<T> implements List<T> {
  noSuchMethod(Invocation invocation) {
    log(invocation);
    super.noSuchMethod(invocation); // Will throw.
  }
}
void main() {
  MockList().add(42);
}

This code has no compile-time warnings or errors even though the MockList class has no concrete implementation of any of the List interface methods. Calls to List methods are forwarded to noSuchMethod, so this code will log an invocation similar to Invocation.method(#add, [42]) and then throw.

If a value is returned from noSuchMethod, it becomes the result of the original invocation. If the value is not of a type that can be returned by the original invocation, a type error occurs at the invocation.

The default behavior is to throw a NoSuchMethodError.

Inherited from Object.

Implementation
dart
@pragma("vm:entry-point")
@pragma("wasm:entry-point")
external dynamic noSuchMethod(Invocation invocation);

orElse() inherited ​

Validated<E, A> orElse(Validated<E, A> Function() orElse)

If this instance is a Valid, this is returned. Otherwise, the result of evaluating orElse is returned.

Inherited from Validated.

Implementation
dart
Validated<E, A> orElse(Function0<Validated<E, A>> orElse) => fold((_) => orElse(), (_) => this);

swap() inherited ​

Validated<A, E> swap()

Returns a new Validated where the invalid and valid types are swapped.

Inherited from Validated.

Implementation
dart
Validated<A, E> swap() => fold((e) => e.valid(), (a) => a.invalid());

toEither() inherited ​

Either<E, A> toEither()

Returns a new Either where the left and right types correspond to the invalid and valid types respectively.

Inherited from Validated.

Implementation
dart
Either<E, A> toEither() => fold((e) => e.asLeft(), (a) => a.asRight());

toIList() inherited ​

IList<A> toIList()

Returns a new IList with the valid value of this instance, if any. If this instance is Invalid, an empty IList is returned.

Inherited from Validated.

Implementation
dart
IList<A> toIList() => fold((_) => nil(), (a) => IList.fromDart([a]));

toOption() inherited ​

Option<A> toOption()

Returns None if this instance is an Invalid, otherwise a Some with the valid value.

Inherited from Validated.

Implementation
dart
Option<A> toOption() => fold((_) => none(), (a) => Some(a));

toString() inherited ​

String toString()

A string representation of this object.

Some classes have a default textual representation, often paired with a static parse function (like int.parse). These classes will provide the textual representation as their string representation.

Other classes have no meaningful textual representation that a program will care about. Such classes will typically override toString to provide useful information when inspecting the object, mainly for debugging or logging.

Inherited from Validated.

Implementation
dart
@override
String toString() => fold((a) => 'Invalid($a)', (b) => 'Valid($b)');

toValidatedNel() inherited ​

ValidatedNel<NonEmptyIList<E>, A> toValidatedNel()

Converts this instance to a ValidatedNel.

Inherited from Validated.

Implementation
dart
ValidatedNel<E, A> toValidatedNel() => fold(Validated.invalidNel, Validated.validNel);

valueOr() inherited ​

A valueOr(A Function(E) f)

Alias for fold.

Inherited from Validated.

Implementation
dart
A valueOr(Function1<E, A> f) => fold(f, identity);

Extension Methods ​

ap() extension ​

ValidatedNel<NonEmptyIList<E>, B> ap<B>(
  ValidatedNel<NonEmptyIList<E>, B Function(A)> f,
)

Applies f to this value if both instance are Valid. Otherwise returns the error if either is Invalid or the accumulation of errors if both are Invalid.

Available on Validated<E, A>, provided by the ValidatedNelOps<E, A> extension

Implementation
dart
ValidatedNel<E, B> ap<B>(ValidatedNel<E, Function1<A, B>> f) {
  return fold(
    (e) => f.fold(
      (ef) => e.concatNel(ef).invalid(),
      (af) => e.invalid(),
    ),
    (a) => f.fold(
      (ef) => ef.invalid(),
      (af) => af(a).validNel<E>(),
    ),
  );
}

flatten() extension ​

Validated<E, A> flatten()

Extracts the nested Validated via fold.

Available on Validated<E, A>, provided by the ValidatedNestedOps<E, A> extension

Implementation
dart
Validated<E, A> flatten() => fold(
  (e) => e.invalid(),
  (va) => va.fold(
    (e) => e.invalid(),
    (a) => a.valid(),
  ),
);

product() extension ​

ValidatedNel<NonEmptyIList<E>, Record> product<B>(
  ValidatedNel<NonEmptyIList<E>, B> that,
)

Returns the product (tuple) of this validation and that if both instances are Valid. Otherwise returns the error if either is Invalid or the accumulation of errors if both are Invalid.

Available on Validated<E, A>, provided by the ValidatedNelOps<E, A> extension

Implementation
dart
ValidatedNel<E, (A, B)> product<B>(ValidatedNel<E, B> that) {
  return fold(
    (e) => that.fold(
      (ef) => e.concatNel(ef).invalid(),
      (af) => e.invalid(),
    ),
    (a) => that.fold(
      (ef) => ef.invalid(),
      (af) => (a, af).validNel<E>(),
    ),
  );
}

Operators ​

operator ==() inherited ​

bool operator ==(Object other)

The equality operator.

The default behavior for all Objects is to return true if and only if this object and other are the same object.

Override this method to specify a different equality relation on a class. The overriding method must still be an equivalence relation. That is, it must be:

  • Total: It must return a boolean for all arguments. It should never throw.

  • Reflexive: For all objects o, o == o must be true.

  • Symmetric: For all objects o1 and o2, o1 == o2 and o2 == o1 must either both be true, or both be false.

  • Transitive: For all objects o1, o2, and o3, if o1 == o2 and o2 == o3 are true, then o1 == o3 must be true.

The method should also be consistent over time, so whether two objects are equal should only change if at least one of the objects was modified.

If a subclass overrides the equality operator, it should override the hashCode method as well to maintain consistency.

Inherited from Validated.

Implementation
dart
@override
bool operator ==(Object other) => fold(
  (e) => other is Invalid<E, A> && other.value == e,
  (a) => other is Valid<E, A> && other.value == a,
);