optional

Documentation

Index

• Variables
• type EmptyConsumer
• type Optional
  • func Empty() Optional
  • func Of(value interface{}) Optional
  • func OfNillable(value interface{}) Optional
  • func (o Optional) Filter(predicate predicate.Predicater) Optional
  • func (o *Optional) FlatMap(mapper func(interface{}) interface{}) Optional
  • func (o Optional) Get() interface{}
  • func (o Optional) IfPresent(action consumer.Consumer)
  • func (o Optional) IfPresentOrElse(action consumer.Consumer, emptyAction EmptyConsumer)
  • func (o Optional) IsPresent() bool
  • func (o Optional) Map(mapper func(interface{}) interface{}) Optional

Variables

var (
	ErrorNoValuePresent = errors.New("no value present")
)

Types

type EmptyConsumer

type EmptyConsumer interface {
	Run()
}

type Optional

type Optional struct {
	// contains filtered or unexported fields
}

Optional is a container object which may or may not contain a non-{@code null} value. If a value is present, {@code isPresent()} returns {@code true}. If no value is present, the object is considered <i>empty</i> and {@code isPresent()} returns {@code false}.

func Empty

func Empty() Optional

Empty returns an empty {@code Optional} instance. No value is present for this {@code Optional}.

func Of

func Of(value interface{}) Optional

Of Returns an {@code Optional} describing the given value.

func OfNillable

func OfNillable(value interface{}) Optional

OfNillable Returns an {@code Optional} describing the given value, if non-{@code null}, otherwise returns an empty {@code Optional}.

func (Optional) Filter

func (o Optional) Filter(predicate predicate.Predicater) Optional

*

• If a value is present, and the value matches the given predicate,
• returns an {@code Optional} describing the value, otherwise returns an
• empty {@code Optional}. *
• @param predicate the predicate to apply to a value, if present
• @return an {@code Optional} describing the value of this
• {@code Optional}, if a value is present and the value matches the
• given predicate, otherwise an empty {@code Optional}
• @throws NullPointerException if the predicate is {@code null}

func (*Optional) FlatMap

func (o *Optional) FlatMap(mapper func(interface{}) interface{}) Optional

*

• If a value is present, returns the result of applying the given
• {@code Optional}-bearing mapping function to the value, otherwise returns
• an empty {@code Optional}. *
• <p>This method is similar to {@link #map(Function)}, but the mapping
• function is one whose result is already an {@code Optional}, and if
• invoked, {@code flatMap} does not wrap it within an additional
• {@code Optional}. *
• @param <U> The type of value of the {@code Optional} returned by the
• mapping function
• @param mapper the mapping function to apply to a value, if present
• @return the result of applying an {@code Optional}-bearing mapping
• function to the value of this {@code Optional}, if a value is
• present, otherwise an empty {@code Optional}
• @throws NullPointerException if the mapping function is {@code null} or
• returns a {@code null} result

func (Optional) Get

func (o Optional) Get() interface{}

Get returns the value if a value is present, otherwise throws {@code ErrorNoValuePresent}.

func (Optional) IfPresent

func (o Optional) IfPresent(action consumer.Consumer)

*

• If a value is present, performs the given action with the value,
• otherwise does nothing. *
• @param action the action to be performed, if a value is present
• @throws ErrorNilPointer if value is present and the given action is
• {@code null}

func (Optional) IfPresentOrElse

func (o Optional) IfPresentOrElse(action consumer.Consumer, emptyAction EmptyConsumer)

*

• If a value is present, performs the given action with the value,
• otherwise performs the given empty-based action. *
• @param action the action to be performed, if a value is present
• @param emptyAction the empty-based action to be performed, if no value is
• present
• @throws NullPointerException if a value is present and the given action
• is {@code null}, or no value is present and the given empty-based
• action is {@code null}.
• @since 9

func (Optional) IsPresent

func (o Optional) IsPresent() bool

IsPresent returns {@code true} if a value is present, otherwise {@code false}.

func (Optional) Map

func (o Optional) Map(mapper func(interface{}) interface{}) Optional

*

• If a value is present, returns an {@code Optional} describing (as if by
• {@link #ofNullable}) the result of applying the given mapping function to
• the value, otherwise returns an empty {@code Optional}. *
• <p>If the mapping function returns a {@code null} result then this method
• returns an empty {@code Optional}. *
• @apiNote
• This method supports post-processing on {@code Optional} values, without
• the need to explicitly check for a return status. For example, the
• following code traverses a stream of URIs, selects one that has not
• yet been processed, and creates a path from that URI, returning
• an {@code Optional<Path>}: *
• <pre>{@code
• Optional<Path> p =
• uris.stream().filter(uri -> !isProcessedYet(uri))
• .findFirst()
• .map(Paths::get);
• }</pre> *
• Here, {@code findFirst} returns an {@code Optional<URI>}, and then
• {@code map} returns an {@code Optional<Path>} for the desired
• URI if one exists. *
• @param mapper the mapping function to apply to a value, if present
• @param <U> The type of the value returned from the mapping function
• @return an {@code Optional} describing the result of applying a mapping
• function to the value of this {@code Optional}, if a value is
• present, otherwise an empty {@code Optional}
• @throws NullPointerException if the mapping function is {@code null}