Left<L, R> class

Represents the failure or error side of an Either.

A Left<L, R> contains a value of type L, typically used to represent an error or exceptional case. This is returned from methods that may fail, instead of throwing exceptions.

Operations like map and flatMap are no-ops on Left, meaning they return the same Left unchanged.

Example:

Either<String, int> result = const Left('Something went wrong');

print(result.isLeft()); // true
print(result.isRight()); // false
print(result.getLeft()); // 'Something went wrong'

Inheritance

Object
Either<L, R>
Left

Constructors

Left(L value): Creates a Left with the given value.
const

Properties

hashCode → int: The hash code for this object.
no setteroverride
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited
value → L: The encapsulated value, typically representing an error or failure.
final

Methods

all(bool test(R right)) → bool: Returns true when this is a Left or when test passes for the Right value.
inherited
bimap<L2, R2>(L2 ifLeft(L left), R2 ifRight(R right)) → Either<L2, R2>: Applies ifLeft or ifRight and returns a new Either with mapped values.
override
contains(R value) → bool: Returns true when this is a Right containing value.
inherited
exists(bool test(R right)) → bool: Returns true when this is a Right and test passes.
inherited
flatMap<R2>(Either<L, R2> f(R right)) → Either<L, R2>: Applies the function f to the value contained in Right, if it exists, and returns a new Either containing the result. If this is a Left, it is returned unchanged.
override
flatMapAsync<R2>(FutureOr<Either<L, R2>> f(R right)) → Future<Either<L, R2>>: Asynchronously applies f to the Right value, if present.
override
fold(B ifLeft(L left), B ifRight(R right)) → B: Applies one of two functions depending on whether this is a Left or Right.
override
foldAsync(FutureOr ifLeft(L left), FutureOr ifRight(R right)) → Future: Asynchronously applies one of two functions depending on the side present.
inherited
getLeft() → L: Returns the Left value if this is a Left, otherwise throws.
override
getOrElse(R orElse(L left)) → R: Returns the Right value if this is a Right, otherwise computes a fallback.
inherited
getOrNull() → R?: Returns the Right value if this is a Right, otherwise null.
inherited
getRight() → R: Returns the Right value if this is a Right, otherwise throws.
override
isLeft() → bool: Returns true if this is a Left.
override
isRight() → bool: Returns true if this is a Right.
override
leftOrNull() → L?: Returns the Left value if this is a Left, otherwise null.
override
map<R2>(R2 f(R right)) → Either<L, R2>: Transforms the value contained in Right using the given function f, returning a new Either with the transformed value.
override
mapAsync<R2>(FutureOr<R2> f(R right)) → Future<Either<L, R2>>: Asynchronously transforms the Right value using f, if present.
override
mapLeft<L2>(L2 f(L left)) → Either<L2, R>: Maps the Left value using f, if present.
override
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
inherited
rightOrNull() → R?: Returns the Right value if this is a Right, otherwise null.
override
swap() → Either<R, L>: Swaps the sides of this Either, turning Left into Right and vice versa.
override
tap(void f(R right)) → Either<L, R>: Runs f with the Right value, if present, and returns this Either.
inherited
tapLeft(void f(L left)) → Either<L, R>: Runs f with the Left value, if present, and returns this Either.
inherited
toString() → String: A string representation of this object.
override

Operators

operator ==(Object other) → bool: The equality operator.
override