【初识Go】| Day11 反射机制

type User struct {
  gorm.Model
  Name         string
  Age          sql.NullInt64
  Birthday     *time.Time
  Email        string  `gorm:"type:varchar(100);unique_index"`
  Role         string  `gorm:"size:255"` // set field size to 255
  MemberNumber *string `gorm:"unique;not null"` // set member number to unique and not null
  Num          int     `gorm:"AUTO_INCREMENT"` // set num to auto incrementable
  Address      string  `gorm:"index:addr"` // create index with name `addr` for address
  IgnoreMe     int     `gorm:"-"` // ignore this field
}

var users []User
db.Find(&users)

func bridge(funcPtr interface{}, args ...interface{})

package main

import (
	"fmt"
	"reflect"
)

func main() {
	var Num float64 = 3.14

	v := reflect.ValueOf(Num)
	t := reflect.TypeOf(Num)

	fmt.Println("Reflect : Num.Value = ", v)
	fmt.Println("Reflect : Num.Type  = ", t)
}

Reflect : Num.Value =  3.14
Reflect : Num.Type  =  float64

func TypeOf(i interface{}) Type
func (v Value) Interface() (i interface{})

package main
import (
    "fmt"
    "reflect"
)
func main() {
    var Num = 3.14
    v := reflect.ValueOf(Num)
    t := reflect.TypeOf(Num)
    fmt.Println(v)
    fmt.Println(t)

    origin := v.Interface().(float64)
    fmt.Println(origin)
}

3.14
float64
3.14

package main
import (
    "reflect"
)
func main() {
        var Num float64 = 3.14
        v := reflect.ValueOf(Num)
        v.SetFloat(6.18)
}

panic: reflect: reflect.Value.SetFloat using unaddressable value

goroutine 1 [running]:
reflect.flag.mustBeAssignableSlow(0x8e)
	/usr/local/go/src/reflect/value.go:259 +0x138
reflect.flag.mustBeAssignable(...)
	/usr/local/go/src/reflect/value.go:246
reflect.Value.SetFloat(0x488ec0, 0xc00001a0b8, 0x8e, 0x4018b851eb851eb8)
	/usr/local/go/src/reflect/value.go:1609 +0x37
main.main()
	/home/ricardo/error.go:8 +0xb3
exit status 2

package main
import (
    "fmt"
    "reflect"
)
func main() {
    var Num float64 = 3.14
    v := reflect.ValueOf(Num)
    fmt.Println("v的可写性:", v.CanSet())
}

var f float64 = 3.41
fmt.Println(f)
p := reflect.ValueOf(&f)
v := p.Elem()
v.SetFloat(6.18)
fmt.Println(f)

package main

import (
        "fmt"
        "reflect"
)

func hello() {
  fmt.Println("Hello world!")
}

func main() {
  hl := hello
  fv := reflect.ValueOf(hl)
  fv.Call(nil)
}

fmt.Printf("%d %s\n", "hello", 42) // "%!d(string=hello) %!s(int=42)"