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optional.go
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optional.go
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package stream
import (
"bytes"
"encoding/json"
)
type Optional[T any] struct {
value T
some bool
}
func Some[T any](value T) Optional[T] {
return Optional[T]{
value: value,
some: true,
}
}
func None[T any]() Optional[T] {
return Optional[T]{some: false}
}
func OptionalFromPointer[T any](ptr *T) Optional[T] {
if ptr == nil {
return None[T]()
}
return Some(*ptr)
}
func FromOptional[T any](opt Optional[T]) Stream[T] {
return Stream[T]{src: opt}
}
func (o Optional[T]) Some() bool { return o.some }
func (o Optional[T]) None() bool { return !o.some }
func (o Optional[T]) Get() (T, bool) { return o.value, o.some }
func (o Optional[T]) MustGet() T {
if o.some {
return o.value
}
panic("Optional[T] is none")
}
func (o Optional[T]) GetOrDefault(defaultVal T) T {
if o.some {
return o.value
}
return defaultVal
}
func (o Optional[T]) GetOrDefaultFunc(defaultFunc func() T) T {
if o.some {
return o.value
}
return defaultFunc()
}
func (o Optional[T]) IfSome(f func(T)) {
if o.some {
f(o.value)
}
}
func (o Optional[T]) IfNone(f func()) {
if !o.some {
f()
}
}
func (o Optional[T]) forEach(f func(T) bool) {
if o.some {
_ = f(o.value)
}
}
func (o Optional[T]) capacityHint() int {
if o.some {
return 1
}
return 0
}
func (o Optional[T]) MarshalJSON() ([]byte, error) {
if o.some {
return json.Marshal(o.value)
}
return []byte("null"), nil
}
func (o *Optional[T]) UnmarshalJSON(data []byte) error {
o.some = false
if bytes.Equal([]byte("null"), data) {
return nil
}
if err := json.Unmarshal(data, &o.value); err != nil {
return err
}
o.some = true
return nil
}