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// 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.
// This file contains the code snippets included in "The Laws of Reflection."
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)
// STOP OMIT
// START f3b OMIT
y := v.Interface().(float64) // y will have type float64.
fmt.Println(y)
// STOP OMIT
// START f3c OMIT
fmt.Println(v.Interface())
// STOP OMIT
// 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)
// STOP OMIT
// 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())
// STOP OMIT
// START f7b OMIT
v := p.Elem()
fmt.Println("settability of v:", v.CanSet())
// STOP OMIT
// 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())
}
// STOP OMIT
// START f8b OMIT
s.Field(0).SetInt(77)
s.Field(1).SetString("Sunset Strip")
fmt.Println("t is now", t)
// STOP OMIT
}
func f9() {
// START f9 OMIT
var x float64 = 3.4
fmt.Println("value:", reflect.ValueOf(x))
// STOP OMIT
}
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