[英]How to update all string fields of arbitrary go struct?
我尝试编写一个函数来更新任意结构的所有字符串字段,如下所示:
type Student struct {
Name string
Age int
}
func SetStringField(obj interface{}) {
reflect.ValueOf(obj).Elem().FieldByName("Name").SetString("set name")
}
func main() {
student := Student{
"alice",
12,
}
SetStringField(&student)
}
但是这个 func 只能更新特定的字段。 我试试这个:
func SetStringField2(obj interface{}) {
// Keys := reflect.TypeOf(obj)
Values := reflect.ValueOf(obj)
count := reflect.ValueOf(obj).NumField()
for i := 0; i < count; i++ {
// fieldKey := Keys.Field(i).Name
fieldValue := Values.Field(i)
switch fieldValue.Kind() {
case reflect.String:
// fieldValue.CanSet()==false
fieldValue.SetString("fieldCleanString2 set name")
// panic: reflect: call of reflect.Value.FieldByName on interface Value
// reflect.ValueOf(&obj).Elem().FieldByName(fieldKey).SetString("123")
}
}
}
func main() {
student := Student{
"alice",
12,
}
SetStringField2(student)
}
并调用 SetStringField2(&student) 得到“恐慌:反映:在 ptr 值上调用reflect.Value.NumField”
那么,还有其他方法可以完成这项工作吗?
问题是反射值不可设置。 要解决此问题,请从指针创建反射值。
// SetStringField2 sets strings fields on the struct pointed to by ps.
func SetStringField2(ps interface{}) {
v := reflect.ValueOf(ps).Elem() // Elem() dereferences pointer
for i := 0; i < v.NumField(); i++ {
fv := v.Field(i)
switch fv.Kind() {
case reflect.String:
fv.SetString("fieldCleanString2 set name")
}
}
}
将指向该值的指针传递给函数:
student := Student{
"alice",
12,
}
SetStringField2(&student)
解决方案1:
package service
import (
"fmt"
"reflect"
"testing"
)
func SetStringField2(obj interface{}) {
Values := reflect.ValueOf(obj).Elem()
count := reflect.Indirect(reflect.ValueOf(obj)).NumField()
for i := 0; i < count; i++ {
fieldValue := Values.Field(i)
switch fieldValue.Kind() {
case reflect.String:
fieldValue.SetString("fieldCleanString2 set name")
}
}
}
func TestSetValue(t *testing.T) {
type Student struct {
Name string
Age int
}
student := &Student{
"alice",
12,
}
SetStringField2(student)
fmt.Print(student.Name)
}
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