mirror of
https://github.com/golang/go
synced 2024-11-22 14:44:50 -07:00
6652b0b866
Originally published on The Go Programming Language Blog, September 6, 2011. http://blog.golang.org/2011/09/laws-of-reflection.html Update #2547 R=golang-dev, r, adg CC=golang-dev https://golang.org/cl/5689054
113 lines
2.2 KiB
Go
113 lines
2.2 KiB
Go
package main
|
|
|
|
import (
|
|
"fmt"
|
|
"reflect"
|
|
)
|
|
|
|
func main() {
|
|
var x float64 = 3.4
|
|
fmt.Println("type:", reflect.TypeOf(x))
|
|
// STOP OMIT
|
|
// TODO(proppy): test output OMIT
|
|
}
|
|
|
|
// STOP main OMIT
|
|
|
|
func f1() {
|
|
// START f1 OMIT
|
|
var x float64 = 3.4
|
|
v := reflect.ValueOf(x)
|
|
fmt.Println("type:", v.Type())
|
|
fmt.Println("kind is float64:", v.Kind() == reflect.Float64)
|
|
fmt.Println("value:", v.Float())
|
|
// STOP OMIT
|
|
}
|
|
|
|
func f2() {
|
|
// START f2 OMIT
|
|
var x uint8 = 'x'
|
|
v := reflect.ValueOf(x)
|
|
fmt.Println("type:", v.Type()) // uint8.
|
|
fmt.Println("kind is uint8: ", v.Kind() == reflect.Uint8) // true.
|
|
x = uint8(v.Uint()) // v.Uint returns a uint64.
|
|
// STOP OMIT
|
|
}
|
|
|
|
func f3() {
|
|
// START f3 OMIT
|
|
type MyInt int
|
|
var x MyInt = 7
|
|
v := reflect.ValueOf(x)
|
|
// START f3b OMIT
|
|
y := v.Interface().(float64) // y will have type float64.
|
|
fmt.Println(y)
|
|
// START f3c OMIT
|
|
fmt.Println(v.Interface())
|
|
// START f3d OMIT
|
|
fmt.Printf("value is %7.1e\n", v.Interface())
|
|
// STOP OMIT
|
|
}
|
|
|
|
func f4() {
|
|
// START f4 OMIT
|
|
var x float64 = 3.4
|
|
v := reflect.ValueOf(x)
|
|
v.SetFloat(7.1) // Error: will panic.
|
|
// STOP OMIT
|
|
}
|
|
|
|
func f5() {
|
|
// START f5 OMIT
|
|
var x float64 = 3.4
|
|
v := reflect.ValueOf(x)
|
|
fmt.Println("settability of v:", v.CanSet())
|
|
// STOP OMIT
|
|
}
|
|
|
|
func f6() {
|
|
// START f6 OMIT
|
|
var x float64 = 3.4
|
|
v := reflect.ValueOf(x)
|
|
// START f6b OMIT
|
|
v.SetFloat(7.1)
|
|
// STOP OMIT
|
|
}
|
|
|
|
func f7() {
|
|
// START f7 OMIT
|
|
var x float64 = 3.4
|
|
p := reflect.ValueOf(&x) // Note: take the address of x.
|
|
fmt.Println("type of p:", p.Type())
|
|
fmt.Println("settability of p:", p.CanSet())
|
|
// START f7b OMIT
|
|
v := p.Elem()
|
|
fmt.Println("settability of v:", v.CanSet())
|
|
// START f7c OMIT
|
|
v.SetFloat(7.1)
|
|
fmt.Println(v.Interface())
|
|
fmt.Println(x)
|
|
// STOP OMIT
|
|
}
|
|
|
|
func f8() {
|
|
// START f8 OMIT
|
|
type T struct {
|
|
A int
|
|
B string
|
|
}
|
|
t := T{23, "skidoo"}
|
|
s := reflect.ValueOf(&t).Elem()
|
|
typeOfT := s.Type()
|
|
for i := 0; i < s.NumField(); i++ {
|
|
f := s.Field(i)
|
|
fmt.Printf("%d: %s %s = %v\n", i,
|
|
typeOfT.Field(i).Name, f.Type(), f.Interface())
|
|
}
|
|
// START f8b OMIT
|
|
s.Field(0).SetInt(77)
|
|
s.Field(1).SetString("Sunset Strip")
|
|
fmt.Println("t is now", t)
|
|
// STOP OMIT
|
|
}
|