opt

package
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 Go to latest Published: Jul 20, 2026 License: MIT Imports: 9 Imported by: 0

Documentation

Overview

Package opt defines 2-state value of T | null.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func CloneOptions 

func CloneOptions[T comparable, Opts ~[]Option[T]](o Opts) Opts

func Equal 

func Equal[T comparable](l, r Option[T]) bool

Equal tests equality of l and r then returns true if they are equal, false otherwise

func EqualEqualer 

func EqualEqualer[T interface{ Equal(t T) bool }](l, r Option[T]) bool

EqualEqualer tests equality of l and r by calling Equal method implemented on l.

func EqualOptions 

func EqualOptions[T comparable, Opts ~[]Option[T]](l, r Opts) bool

EqualOptions tests equality of l and r then returns true if they are equal, false otherwise

func EqualOptionsEqualer 

func EqualOptionsEqualer[T interface{ Equal(t T) bool }, Opts ~[]Option[T]](l, r Opts) bool

EqualEqualer tests equality of l and r by calling Equal method implemented on l.

func EqualOptionsFunc 

func EqualOptionsFunc[T any, Opts ~[]Option[T]](l, r Opts, cmp func(i, j T) bool) bool

EqualOptionsFunc tests equality of l and r using cmp then returns true if they are equal, false otherwise.

Types

type Option 

type Option[T any] struct {
	// contains filtered or unexported fields
}

Option represents an optional value.

func Assert 

func Assert[T any](v any) Option[T]

Assert type-asserts v into T. If v's internal value is T then returns Some of that value, None otherwise.

func CloneCloner 

func CloneCloner[T interface{ Clone() T }](o Option[T]) Option[T]

CloneCloner clones o by calling the Clone method on its inner value if o is some.

For a custom clone function, use Option.CloneFunc. An Option[T] whose T only needs a shallow copy can be copied by plain assignment.

func Flatten 

func Flatten[T any](o Option[Option[T]]) Option[T]

Flatten converts Option[Option[T]] into Option[T].

func FromOk 

func FromOk[T any](t T, ok bool) Option[T]

FromOk converts conventional (t T, ok bool) into an option. The options is some if ok is true, none otherwise.

For getting values from maps or slices, instead you may want to use IndexMap, IndexSlice respectively.

func FromPointer 

func FromPointer[T any](t *T) Option[T]

FromPointer converts *T into Option[T]. If v is nil, it returns a none Option. Otherwise, it returns some Option whose value is the dereferenced v.

If you need to keep t as pointer, use WrapPointer instead.

func FromSqlNull 

func FromSqlNull[T any](v sql.Null[T]) Option[T]

func IndexMap 

func IndexMap[M ~map[K]V, K comparable, V any](m M, key K) Option[V]

IndexMap gets a value associated with key. If key has a value, the Option is some wrapping the value. Otherwise it returns none Option.

func IndexSlice 

func IndexSlice[S ~[]T, T any](s S, idx int) Option[T]

GetMap gets a value associated with idx. If idx is within interval [0, len(s)), then the Option is some wrapping a value associated to the idx. Otherwise it returns none Option.

func None 

func None[T any]() Option[T]

func Some 

func Some[T any](v T) Option[T]

func WrapPointer 

func WrapPointer[T any](t *T) Option[*T]

WrapPointer converts *T into Option[*T]. The option is some if t is non nil, none otherwise.

If you want t to be dereferenced, use FromPointer instead.

func (Option[T]) And 

func (o Option[T]) And[U any](u Option[U]) Option[U]

And returns u if o is some, otherwise None[T].

func (Option[T]) AndThen 

func (o Option[T]) AndThen[U any](f func(t T) Option[U]) Option[U]

AndThen calls f with value of o if o is some, otherwise returns None[T].

func (Option[T]) CloneFunc 

func (o Option[T]) CloneFunc(cloneT func(T) T) Option[T]

CloneFunc clones o using the cloneT function.

func (Option[T]) EqualFunc 

func (o Option[T]) EqualFunc(other Option[T], cmp func(i, j T) bool) bool

EqualFunc tests o and other if both are Some or None. If their state does not match, it returns false immediately. If both have value, it tests equality of their values by cmp.

If T is just a comparable type, use Equal. If T is an implementor of interface { Equal(t T) bool }, e.g time.Time, use EqualEqualer.

func (Option[T]) Expect 

func (o Option[T]) Expect(msg string) T

Expect returns o's value if o is some. Otherwise it panics with msg.

func (Option[T]) Filter 

func (o Option[T]) Filter(pred func(t T) bool) Option[T]

Filter returns o if o is some and calling pred against o's value returns true. Otherwise it returns None[T].

func (*Option[T]) GetOrInsert 

func (o *Option[T]) GetOrInsert(t T) *T

GetOrInsert inserts t into o if o is none, then returns a pointer to o's value. If o is already some, the existing value is kept and t is discarded.

o must be addressable; the returned pointer aliases o's internal value.

func (*Option[T]) GetOrInsertDefault 

func (o *Option[T]) GetOrInsertDefault() *T

GetOrInsertDefault inserts the zero value of T into o if o is none, then returns a pointer to o's value. If o is already some, the existing value is kept.

o must be addressable; the returned pointer aliases o's internal value.

func (*Option[T]) GetOrInsertFunc 

func (o *Option[T]) GetOrInsertFunc(fn func() T) *T

GetOrInsertFunc inserts the result of fn into o if o is none, then returns a pointer to o's value. If o is already some, the existing value is kept and fn is not called.

o must be addressable; the returned pointer aliases o's internal value.

func (*Option[T]) Insert 

func (o *Option[T]) Insert(t T) *T

Insert sets o's value to t, overwriting any existing value, and returns a pointer to it.

See Option.GetOrInsert which only inserts when o is none.

o must be addressable; the returned pointer aliases o's internal value.

func (Option[T]) Inspect 

func (o Option[T]) Inspect(fn func(t T)) Option[T]

Inspect calls fn with o's value if o is some, then returns o unchanged.

func (Option[T]) IsNone 

func (o Option[T]) IsNone() bool

func (Option[T]) IsNoneOr 

func (o Option[T]) IsNoneOr(fn func(T) bool) bool

IsNoneOr returns true if o is none, or if o is some and calling fn with o's value returns true.

func (Option[T]) IsSome 

func (o Option[T]) IsSome() bool

func (Option[T]) IsSomeAnd 

func (o Option[T]) IsSomeAnd(fn func(T) bool) bool

IsSomeAnd returns true if o is some and calling f with value of o returns true. Otherwise it returns false.

func (Option[T]) IsZero 

func (o Option[T]) IsZero() bool

func (Option[T]) Iter 

func (o Option[T]) Iter() iter.Seq[T]

Iter returns an iterator over the internal value. If o is some, the iterator yields the Option.Value(), otherwise nothing.

func (Option[T]) LogValue 

func (o Option[T]) LogValue() slog.Value

LogValue implements slog.LogValuer

func (Option[T]) Map 

func (o Option[T]) Map[U any](f func(T) U) Option[U]

Map returns Some[U] whose inner value is o's value mapped by f if o is some. Otherwise it returns None[U].

func (Option[T]) MapOr 

func (o Option[T]) MapOr[U any](defaultValue U, f func(T) U) U

MapOr returns o's value applied by f if o is some. Otherwise it returns defaultValue.

func (Option[T]) MapOrElse 

func (o Option[T]) MapOrElse[U any](defaultFn func() U, fn func(T) U) U

MapOrElse returns o's value applied by fn if o is some. Otherwise it returns the result of defaultFn.

func (Option[T]) MarshalJSON 

func (o Option[T]) MarshalJSON() ([]byte, error)

func (Option[T]) MarshalJSONTo 

func (o Option[T]) MarshalJSONTo(enc *jsontext.Encoder) error

MarshalJSONTo implements encoding/json/v2.MarshalerTo.

It encodes a none Option as the JSON null and a some Option as its inner value.

func (Option[T]) MarshalXML 

func (o Option[T]) MarshalXML(e *xml.Encoder, start xml.StartElement) error

func (Option[T]) Or 

func (o Option[T]) Or(u Option[T]) Option[T]

Or returns o if o is some, otherwise u.

func (Option[T]) OrElse 

func (o Option[T]) OrElse(f func() Option[T]) Option[T]

OrElse returns o if o is some, otherwise calls f and returns the result.

func (*Option[T]) Pointer 

func (o *Option[T]) Pointer() *T

Pointer transforms o to *T, the plain conventional Go representation of an optional value. The pointer is reference to internal value. Use lock mechanism if multiple goroutines need to acccess it.

func (Option[T]) SqlNull 

func (o Option[T]) SqlNull() sql.Null[T]

func (*Option[T]) UnmarshalJSON 

func (o *Option[T]) UnmarshalJSON(data []byte) error

func (*Option[T]) UnmarshalJSONFrom 

func (o *Option[T]) UnmarshalJSONFrom(dec *jsontext.Decoder) error

UnmarshalJSONFrom implements encoding/json/v2.UnmarshalerFrom.

It decodes the JSON null as a none Option and any other JSON value as a some Option.

func (*Option[T]) UnmarshalXML 

func (o *Option[T]) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error

func (Option[T]) Unwrap 

func (o Option[T]) Unwrap() T

Unwrap returns o's value if o is some. Otherwise it panics.

func (Option[T]) UnwrapOr 

func (o Option[T]) UnwrapOr(t T) T

UnwrapOr returns o's value if o is some, otherwise t.

func (Option[T]) UnwrapOrDefault 

func (o Option[T]) UnwrapOrDefault() T

UnwrapOrDefault returns o's value if o is some, otherwise the zero value of T.

func (Option[T]) UnwrapOrElse 

func (o Option[T]) UnwrapOrElse(fn func() T) T

UnwrapOrElse returns o's value if o is some, otherwise the result of fn.

func (Option[T]) Value 

func (o Option[T]) Value() T

Value returns its internal as T. T would be zero value if o is None.

func (Option[T]) Xor 

func (o Option[T]) Xor(u Option[T]) Option[T]

Xor returns o or u if either is some. If both are some or both none, it returns None[T].

type Options 

type Options[T any] []Option[T]

func (Options[T]) CloneFunc 

func (o Options[T]) CloneFunc(cloneT func(T) T) Options[T]

func (Options[T]) EqualFunc 

func (o Options[T]) EqualFunc(opts Options[T], cmp func(i, j T) bool) bool

EqualFunc tests equality of l and r using an equality function cmp.

If T is just a comparable type, use EqualOptions. If T is an implementor of interface { Equal(t T) bool }, e.g time.Time, use EqualOptionsEqualer.

func (Options[T]) Iter 

func (o Options[T]) Iter() iter.Seq[Option[T]]

type SqlNull 

type SqlNull[T any] struct {
	Option[T]
}

SqlNull[T] adapts Option[T] to sql.Scanner and driver.Valuer.

func (*SqlNull[T]) Scan 

func (n *SqlNull[T]) Scan(src any) error

Scan implements sql.Scanner.

If T or *T implements sql.Scanner, the implementation is used. Otherwise, SqlNull[T] falls back to sql.Null[T] as sql.Scanner.

func (SqlNull[T]) Value 

func (n SqlNull[T]) Value() (driver.Value, error)

Value implements driver.Valuer.

If T or *T implements driver.Valuer, the implementation is used. In this respect, T should not be a pointer type or Option[T] should not store nil value. Otherwise, SqlNull[T] falls back to sql.Null[T] as driver.Valuer.

Source Files

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