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 setter, override

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

value → L

The encapsulated value, typically representing an error or failure.

final

Methods

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

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

fold<B>(B ifLeft(L left), B ifRight(R right)) → B

Applies one of two functions depending on whether this is a Left or Right.

override

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

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

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

toString() → String

A string representation of this object.

override

Operators

operator ==(Object other) → bool

The equality operator.

override