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
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
|
// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package reflect_test
import (
"fmt"
"reflect"
)
func ExampleMakeFunc() {
// swap is the implementation passed to MakeFunc.
// It must work in terms of reflect.Values so that it is possible
// to write code without knowing beforehand what the types
// will be.
swap := func(in []reflect.Value) []reflect.Value {
return []reflect.Value{in[1], in[0]}
}
// makeSwap expects fptr to be a pointer to a nil function.
// It sets that pointer to a new function created with MakeFunc.
// When the function is invoked, reflect turns the arguments
// into Values, calls swap, and then turns swap's result slice
// into the values returned by the new function.
makeSwap := func(fptr interface{}) {
// fptr is a pointer to a function.
// Obtain the function value itself (likely nil) as a reflect.Value
// so that we can query its type and then set the value.
fn := reflect.ValueOf(fptr).Elem()
// Make a function of the right type.
v := reflect.MakeFunc(fn.Type(), swap)
// Assign it to the value fn represents.
fn.Set(v)
}
// Make and call a swap function for ints.
var intSwap func(int, int) (int, int)
makeSwap(&intSwap)
fmt.Println(intSwap(0, 1))
// Make and call a swap function for float64s.
var floatSwap func(float64, float64) (float64, float64)
makeSwap(&floatSwap)
fmt.Println(floatSwap(2.72, 3.14))
// Output:
// 1 0
// 3.14 2.72
}
func ExampleStructTag() {
type S struct {
F string `species:"gopher" color:"blue"`
}
s := S{}
st := reflect.TypeOf(s)
field := st.Field(0)
fmt.Println(field.Tag.Get("color"), field.Tag.Get("species"))
// Output:
// blue gopher
}
|
