1 // Copyright 2012 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // This file contains the code snippets included in "The Laws of Reflection." 6 7 package main 8 9 import ( 10 "fmt" 11 "reflect" 12 ) 13 14 func main() { 15 var x float64 = 3.4 16 fmt.Println("type:", reflect.TypeOf(x)) 17 // STOP OMIT 18 // TODO(proppy): test output OMIT 19 } 20 21 // STOP main OMIT 22 23 func f1() { 24 // START f1 OMIT 25 var x float64 = 3.4 26 v := reflect.ValueOf(x) 27 fmt.Println("type:", v.Type()) 28 fmt.Println("kind is float64:", v.Kind() == reflect.Float64) 29 fmt.Println("value:", v.Float()) 30 // STOP OMIT 31 } 32 33 func f2() { 34 // START f2 OMIT 35 var x uint8 = 'x' 36 v := reflect.ValueOf(x) 37 fmt.Println("type:", v.Type()) // uint8. 38 fmt.Println("kind is uint8: ", v.Kind() == reflect.Uint8) // true. 39 x = uint8(v.Uint()) // v.Uint returns a uint64. 40 // STOP OMIT 41 } 42 43 func f3() { 44 // START f3 OMIT 45 type MyInt int 46 var x MyInt = 7 47 v := reflect.ValueOf(x) 48 // STOP OMIT 49 // START f3b OMIT 50 y := v.Interface().(float64) // y will have type float64. 51 fmt.Println(y) 52 // STOP OMIT 53 // START f3c OMIT 54 fmt.Println(v.Interface()) 55 // STOP OMIT 56 // START f3d OMIT 57 fmt.Printf("value is %7.1e\n", v.Interface()) 58 // STOP OMIT 59 } 60 61 func f4() { 62 // START f4 OMIT 63 var x float64 = 3.4 64 v := reflect.ValueOf(x) 65 v.SetFloat(7.1) // Error: will panic. 66 // STOP OMIT 67 } 68 69 func f5() { 70 // START f5 OMIT 71 var x float64 = 3.4 72 v := reflect.ValueOf(x) 73 fmt.Println("settability of v:", v.CanSet()) 74 // STOP OMIT 75 } 76 77 func f6() { 78 // START f6 OMIT 79 var x float64 = 3.4 80 v := reflect.ValueOf(x) 81 // STOP OMIT 82 // START f6b OMIT 83 v.SetFloat(7.1) 84 // STOP OMIT 85 } 86 87 func f7() { 88 // START f7 OMIT 89 var x float64 = 3.4 90 p := reflect.ValueOf(&x) // Note: take the address of x. 91 fmt.Println("type of p:", p.Type()) 92 fmt.Println("settability of p:", p.CanSet()) 93 // STOP OMIT 94 // START f7b OMIT 95 v := p.Elem() 96 fmt.Println("settability of v:", v.CanSet()) 97 // STOP OMIT 98 // START f7c OMIT 99 v.SetFloat(7.1) 100 fmt.Println(v.Interface()) 101 fmt.Println(x) 102 // STOP OMIT 103 } 104 105 func f8() { 106 // START f8 OMIT 107 type T struct { 108 A int 109 B string 110 } 111 t := T{23, "skidoo"} 112 s := reflect.ValueOf(&t).Elem() 113 typeOfT := s.Type() 114 for i := 0; i < s.NumField(); i++ { 115 f := s.Field(i) 116 fmt.Printf("%d: %s %s = %v\n", i, 117 typeOfT.Field(i).Name, f.Type(), f.Interface()) 118 } 119 // STOP OMIT 120 // START f8b OMIT 121 s.Field(0).SetInt(77) 122 s.Field(1).SetString("Sunset Strip") 123 fmt.Println("t is now", t) 124 // STOP OMIT 125 } 126 127 func f9() { 128 // START f9 OMIT 129 var x float64 = 3.4 130 fmt.Println("value:", reflect.ValueOf(x)) 131 // STOP OMIT 132 } 133
