github.com/neohugo/neohugo@v0.123.8/common/hcontext/context.go (about)

     1  // Copyright 2024 The Hugo Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  // http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package hcontext
    15  
    16  import "context"
    17  
    18  // ContextDispatcher is a generic interface for setting and getting values from a context.
    19  type ContextDispatcher[T any] interface {
    20  	Set(ctx context.Context, value T) context.Context
    21  	Get(ctx context.Context) T
    22  }
    23  
    24  // NewContextDispatcher creates a new ContextDispatcher with the given key.
    25  func NewContextDispatcher[T any, R comparable](key R) ContextDispatcher[T] {
    26  	return keyInContext[T, R]{
    27  		id: key,
    28  	}
    29  }
    30  
    31  type keyInContext[T any, R comparable] struct {
    32  	zero T
    33  	id   R
    34  }
    35  
    36  func (f keyInContext[T, R]) Get(ctx context.Context) T {
    37  	v := ctx.Value(f.id)
    38  	if v == nil {
    39  		return f.zero
    40  	}
    41  	return v.(T)
    42  }
    43  
    44  func (f keyInContext[T, R]) Set(ctx context.Context, value T) context.Context {
    45  	return context.WithValue(ctx, f.id, value)
    46  }