option library

Classes

None<A>

Represents a missing value.

Option<T>

Represents a value that could be missing - an [option]al value.

Some<A>

Represents a present value. The value property contains the wrapped value.

Constants

kNone → const Option<Never>

A constant version on None, as Option<Never>.

Functions

alt<T>(Lazy<Option<T>> f) → Option<T> Function(Option<T> option)

If the Option is a None, then the result of the given function will determine the [alt]ernate / replacement Option.

chainNullableK<A, B>(B? f(A value)) → Option<B> Function(Option<A> option)

Returns an function that transforms an Option. If the given transformer returns null, then None is returned.

chainTryCatchK<A, B>(B f(A value)) → Option<B> Function(Option<A> a)

A variant of tryCatchK, that allows for passing in an Option. If the Option is Some, then the value is unwrapped and passed into the function.

Do<A>(DoFunction<A> f) → Option<A>

filter<T>(bool predicate(T value)) → Option<T> Function(Option<T> option)

Using the given predicate, conditionally convert the Option to a None.

flatMap<A, B>(Option<B> f(A value)) → Option<B> Function(Option<A> option)

Transform the Option into another Option, using the given function.

flatMapTuple2<A, A2>(Option<A2> f(A a)) → Option Function(Option<A> o)

A variant of flatMap that appends the result to a tuple.

flatMapTuple3<A, A2, A3>(Option<A3> f(dynamic a)) → Option<Tuple3<A, A2, A3>> Function(Option o)

A variant of flatMap that appends the result to a tuple.

flatten<A>(Option<Option<A>> option) → Option<A>

Flatten's nested Option to a single level.

fold<A, B>(B ifNone(), B ifSome(A value)) → B Function(Option<A> option)

Transforms an Option into a value, using the ifNone and ifSome functions.

fromEither<L, R>(Either<L, R> either) → Option<R>

Transforms an Either into an Option. Right becomes Some, and Left becomes None.

fromNullable<T>(T? value) → Option<T>

Returns an Option that returns Some or None, depending on whether it is null or not.

fromNullableK<A, B>(B? f(A value)) → Option<B> Function(A value)

Returns an function that transforms a value and can return a nullable result. If the result is null, then None is returned. Otherwise it is wrapped in Some.

fromNullableWith<T>() → Option<T> Function(T? value)

A wrapper around fromNullable, that allows the type to be enforced. Useful for function composition.

fromPredicate<T>(T value, bool predicate(T value)) → Option<T>

Returns a Some or None if the predicate returns true or false respectively.

fromPredicateK<T>(bool predicate(T value)) → Option<T> Function(T value)

Wrapper around fromPredicate that can be curried with the value.

getOrElse<T>(Lazy<T> orElse) → T Function(Option<T> option)

Unwrap the Option's value if it is Some, otherwise it calls the orElse function to determine the fallback value.

isNone<T>(Option<T> option) → bool

Returns true if the Option is a None.

isSome<T>(Option<T> option) → bool

Returns true if the Option is a Some.

map<T, R>(R f(T value)) → Option<R> Function(Option<T> option)

Transform the wrapped value if the Option is a Some, using the provided function.

map2<A, B, R>(R f(A a, B b)) → Option<R> Function(Option<A> optionA, Option<B> optionB)

Creates a function that accepts two Option's, and if both of them are Some, then the transformer function is called with the unwrapped values.

map2K<A, B, R>(Option<B> optionB, R f(A a, B b)) → Option<R> Function(Option<A> optionA)

A wrapper around map2, useful for chaining. The second Option is passed as the first argument.

map3<A, B, C, R>(R f(A a, B b, C c)) → Option<R> Function(Option<A> optionA, Option<B> optionB, Option<C> optionC)

Creates a function that accepts three Option's, and if they are all Some, then the transformer function is called with the unwrapped values.

map3K<A, B, C, R>(Option<B> optionB, Option<C> optionC, R f(A a, B b, C c)) → Option<R> Function(Option<A> optionA)

A wrapper around map3, useful for chaining. The remaining Option's are passed as arguments.

mapTuple2<A, B, R>(R f(A a, B b)) → Option<R> Function(dynamic tuple)

A variant of map2, that accepts the two Option's as a Tuple2.

mapTuple3<A, B, C, R>(R f(A a, B b, C c)) → Option<R> Function(Tuple3<Option<A>, Option<B>, Option<C>> tuple)

A variant of map3, that accepts the Option's as a Tuple3.

none<T>() → Option<T>

Returns an Option that resolves to a None. Represents a value that does not exists.

some<T>(T value) → Option<T>

Returns an Option that resolves to a Some, which wraps the given value. Represents a value that does exist.

tap<A>(void f(A value)) → Option<A> Function(Option<A> option)

Execute a side effect on the wrapped value, if the Option is a Some.

toNullable<T>(Option<T> option) → T?

Transforms the Option into a nullable value. Some unwraps to the value, while None becomes null.

traverse<A, B>(Option<B> f(A a)) → Option<IList<B>> Function(Iterable<A>)

tryCatch<T>(T f()) → Option<T>

Returns the value as a Some if the function succeeds. If it raises an exception, then it will return None.

tryCatchK<A, B>(B f(A value)) → Option<B> Function(A a)

A variant of tryCatch, that allows for passing in external values.

Typedefs

DoFunction<A> = A Function(_DoAdapter $)