go-lemmy/types/optional.go

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2022-12-10 17:17:16 +00:00
package types
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"net/url"
)
var ErrOptionalEmpty = errors.New("optional value is empty")
type Optional[T any] struct {
value *T
}
func NewOptional[T any](v T) Optional[T] {
return Optional[T]{value: &v}
}
func NewOptionalPtr[T any](v *T) Optional[T] {
return Optional[T]{value: v}
}
func NewOptionalNil[T any]() Optional[T] {
return Optional[T]{}
}
func (o Optional[T]) Set(v T) Optional[T] {
o.value = &v
return o
}
func (o Optional[T]) SetPtr(v *T) Optional[T] {
o.value = v
return o
}
func (o Optional[T]) SetNil() Optional[T] {
o.value = nil
return o
}
func (o Optional[T]) IsValid() bool {
return o.value != nil
}
func (o Optional[T]) MustValue() T {
if o.value == nil {
panic("optional value is nil")
}
return *o.value
}
func (o Optional[T]) Value() (T, error) {
if o.value != nil {
return *o.value, ErrOptionalEmpty
}
return *new(T), nil
}
func (o Optional[T]) ValueOr(fallback T) T {
if o.value != nil {
return *o.value
}
return fallback
}
func (o Optional[T]) MarshalJSON() ([]byte, error) {
return json.Marshal(o.value)
}
func (o *Optional[T]) UnmarshalJSON(b []byte) error {
if bytes.Equal(b, []byte("null")) {
o.value = nil
return nil
}
o.value = new(T)
return json.Unmarshal(b, o.value)
}
func (o Optional[T]) EncodeValues(key string, v *url.Values) error {
s := o.String()
if s != "<nil>" {
v.Set(key, s)
}
return nil
}
func (o Optional[T]) String() string {
if o.value == nil {
return "<nil>"
}
return fmt.Sprint(*o.value)
}
func (o Optional[T]) GoString() string {
if o.value == nil {
return "nil"
}
return fmt.Sprintf("%#v", *o.value)
}