1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
// Copyright 2024 Bjørn Erik Pedersen
// SPDX-License-Identifier: MIT
package contexthelpers
import "context"
// ContextDispatcher is a generic interface for setting and getting values from context.Context.
type ContextDispatcher[T any] interface {
// Set stores the value in the context and returns a new context.
Set(ctx context.Context, value T) context.Context
// Get retrieves the value from the context. If the value is not set, it returns the zero value of T.
Get(ctx context.Context) T
// Lookup retrieves the value from the context and returns a boolean indicating if the value was found.
Lookup(ctx context.Context) (T, bool)
}
// NewContextDispatcher creates a new ContextDispatcher with the given key.
func NewContextDispatcher[T any, R comparable](key R) ContextDispatcher[T] {
return keyInContext[T, R]{
id: key,
}
}
type keyInContext[T any, R comparable] struct {
zero T
id R
}
func (f keyInContext[T, R]) Get(ctx context.Context) T {
v := ctx.Value(f.id)
if v == nil {
return f.zero
}
return v.(T)
}
func (f keyInContext[T, R]) Lookup(ctx context.Context) (T, bool) {
v := ctx.Value(f.id)
if v == nil {
return f.zero, false
}
return v.(T), true
}
func (f keyInContext[T, R]) Set(ctx context.Context, value T) context.Context {
return context.WithValue(ctx, f.id, value)
}
|
