GolangrpcormjsonruntimeGolangGolangreflectreflectfunc TestReflect_Integer(t *testing.T) {
i := 1
v := reflect.ValueOf(i)
vKind := v.Kind()
vType := v.Type()
t.Logf("i kind: %+v\n", vKind)
t.Logf("i type: %+v\n", vType)
itf := v.Interface()
j, ok := itf.(int)
t.Logf("j val: %+v\n", j)
if !ok || j != i {
t.Fatalf("i != j")
}
}
reflect.ValueOfinterface{}anyreflect.Valuereflect.ValuetypptrflagKindTypereflect.Valueflagtypreflect.ValueInterfaceinterface{}.(int)reflectrpcreflect.ValueFunc.CallexampleUserUserInfojsonToStringResponsetype UserInfo struct {
Desc string `json:"desc"`
City string `json:"city" desc:"the city of user"`
}
type User struct {
ID int `json:"id"`
Name string `json:"name"`
Info *UserInfo `json:"info"`
}
func (u *User) ToString() string {
return fmt.Sprintf("[%d]%s", u.ID, u.Name)
}
func (u *User) Response(from string, msg string) string {
return fmt.Sprintf("User %s received msg %s from <%s>", u.ToString(), msg, from)
}
Responsefunc TestReflect_Method(t *testing.T) {
u := &User{1, "jack", nil}
uPtr := reflect.ValueOf(u)
// MethodByName：获取特定名字的Method
meth, ok := uPtr.Type().MethodByName("Response")
if !ok {
t.Fatalf("no method named Response")
}
t.Logf("meth Response: %+v\n", meth)
methType := meth.Type
// 入参3个：User实例、from、msg
if methType.NumIn() != 3 {
t.Fatalf("invalid NumIn %d, expected %d", methType.NumIn(), 3)
}
// 返回值1个：response string
if methType.NumOut() != 1 {
t.Fatalf("invalid NumOut %d, expected %d", methType.NumOut(), 1)
}
// 通过Func.Call得到返回值list
from, msg := reflect.ValueOf("client"), reflect.ValueOf("ping")
rets := meth.Func.Call([]reflect.Value{uPtr, from, msg})
if len(rets) != 1 {
t.Fatalf("invalid num rets %d, expected %d", len(rets), 1)
}
// 返回1个string对象
respVal := rets[0]
if respVal.Type() != reflect.TypeOf("") {
t.Fatalf("invalid ret type %v, expected %s", respVal.Type(), "STRING")
}
resp, ok := respVal.Interface().(string)
if !ok {
t.Fatalf("ret value cannot be converted to string")
}
t.Logf("resp: %s\n", resp)
}
MethodByNameFunc.Callreflect.Indirect(反射值)反射值.Elem()exampleToStringResponseToStringfunc TestReflect_Pointer(t *testing.T) {
u := &User{1, "jack", nil}
vPtr := reflect.ValueOf(u)
vPtrKind := vPtr.Kind()
vPtrType := vPtr.Type()
t.Logf("ptr kind: %+v\n", vPtrKind)
t.Logf("ptr type: %+v\n", vPtrType)
meth, ok := vPtrType.MethodByName("ToString")
t.Logf("ptr meth ToString: %+v (%+v)\n", meth, ok)
vVal := reflect.Indirect(vPtr)
// vVal := vPtr.Elem()
vValKind := vVal.Kind()
vValType := vVal.Type()
t.Logf("val kind: %+v\n", vValKind)
t.Logf("val type: %+v\n", vValType)
meth, ok = vValType.MethodByName("ToString")
t.Logf("val meth ToString: %+v (%+v)\n", meth, ok)
}
slicemapreflect.Valueslicemapfunc TestReflect_CopySliceAndMap(t *testing.T) {
mp := map[string]int{
"jack": 1,
"tom": 2,
}
sl := []int{1, 1, 2, 3, 5, 8}
vals := []reflect.Value{reflect.ValueOf(mp), reflect.ValueOf(sl)}
var copyVals []reflect.Value
for _, val := range vals {
var copyVal reflect.Value
switch val.Kind() {
case reflect.Map:
// MakeMap：创建map实例
copyVal = reflect.MakeMap(val.Type())
// MapRange：获取map对象的Iterator
iter := val.MapRange()
for iter.Next() {
copyVal.SetMapIndex(iter.Key(), iter.Value())
}
case reflect.Slice:
// AppendSlice：在一个slice的基础上extend另一个slice
copyVal = reflect.AppendSlice(
reflect.MakeSlice(val.Type(), 0, val.Len()),
val)
}
copyVals = append(copyVals, copyVal)
}
// 通过DeepEqual方法，可以做值的相等性比较
for _, val := range copyVals {
switch val.Kind() {
case reflect.Map:
if val.Len() != len(mp) {
t.Fatalf("invalid map length %d, expected %d", val.Len(), len(mp))
}
copyVal, ok := val.Interface().(map[string]int)
if !ok {
t.Fatalf("map convert failed")
}
t.Logf("copied map: %+v", copyVal)
for k, v := range mp {
copyV, ok := copyVal[k]
if !ok || !reflect.DeepEqual(v, copyV) {
t.Fatalf("copy value of key %s failed, expected %d, actual %d", k, v, copyV)
}
}
case reflect.Slice:
if val.Len() != len(sl) {
t.Fatalf("invalid slice length %d, expected %d", val.Len(), len(sl))
}
copyVal, ok := val.Interface().([]int)
if !ok {
t.Fatalf("slice convert failed")
}
t.Logf("copied slice: %+v", copyVal)
if !reflect.DeepEqual(copyVal, sl) {
t.Fatalf("slice not equal")
}
}
}
}
reflectstructreflect.Value.Type()TypeTypejsonormexamplefunc TestReflect_Struct(t *testing.T) {
st := reflect.ValueOf(&User{
ID: 9,
Name: "Ronaldo",
Info: &UserInfo{
Desc: "SC",
City: "Madrid",
},
}).Elem().Type()
// 多少个字段
numField := st.NumField()
t.Logf("num fields: %d", numField)
// 一个个字段遍历，输出字段名字、数据类型、json标注
for i := 0; i < numField; i++ {
field := st.Field(i)
t.Logf("field %d -> name: %s, type: %v, json: %s",
i+1,
field.Name,
field.Type,
field.Tag.Get("json"))
}
// 嵌套的字段，用FieldByIndex可以定位到
cityField := st.FieldByIndex([]int{2, 1})
// 按照上面UserInfo.City的定义，拿取desc标注信息
cityFieldDesc, ok := cityField.Tag.Lookup("desc")
if !ok {
t.Fatalf("cannot find city field desc")
}
t.Logf("CityField -> name: %s, type: %v, desc: %s",
cityField.Name,
cityField.Type,
cityFieldDesc)
}
可以看到，我们可以很方便拿到结构体的定义信息，更加深层嵌套的定义信息也都能拿到。可以说，太灵活了！