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optional.go
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optional.go
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/*
* SPDX-FileCopyrightText: Copyright (c) 2003 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package gontainer
import (
"reflect"
"unsafe"
)
// Optional defines optional service dependency.
type Optional[T any] struct {
value T
}
// Get returns optional service instance.
func (o Optional[T]) Get() T {
return o.value
}
// Optional marks this type as optional.
func (o Optional[T]) Optional() {}
// isOptionalType checks and returns optional box type.
func isOptionalType(typ reflect.Type) (reflect.Type, bool) {
if typ.Kind() == reflect.Struct {
if _, ok := typ.MethodByName("Optional"); ok {
if methodValue, ok := typ.MethodByName("Get"); ok {
if methodValue.Type.NumOut() == 1 {
methodType := methodValue.Type.Out(0)
return methodType, true
}
}
}
}
return nil, false
}
// newOptionalValue creates new optional type with a value.
func newOptionalValue(typ reflect.Type, value reflect.Value) reflect.Value {
// Prepare boxing struct for value.
box := reflect.New(typ).Elem()
// Inject factory output value to the boxing struct.
field := box.FieldByName("value")
pointer := unsafe.Pointer(field.UnsafeAddr())
public := reflect.NewAt(field.Type(), pointer)
public.Elem().Set(value)
return box
}