文章目录
golang结构体中使用tag标记简介语法结构快速入门常见应用应用json编码应用xml编码应用form表单绑定gin框架form和数据绑定golang结构体中使用tag标记
简介
我们可以在结构体的字段后面，添加一些对该字段的说明（元信息meta），程序通过反射解析这些信息并使用。
语法结构
`key:"value" key:"value"`
反引号括起来，key不加双引号，value加双引号，多个值中间用空格分开
快速入门
package mainimport ("fmt""reflect")func main() {type S struct {F string `species:"gopher" color:"blue"`}//实例化结构体,在这里没有使用到，所以空实例化s := S{}//使用反射获得结构体的type类型st := reflect.TypeOf(s)//拿到第一个字段field := st.Field(0)//拿到tag里面的东西fmt.Println(field.Tag.Get("color"), field.Tag.Get("species"))}
运行结果：
[Running] go run "e:\golang开发学习\go_pro\main.go"blue gopher[Done] exited with code=0 in 1.234 seconds
常见应用
应用json编码
package mainimport ("encoding/json""fmt""log""os""time")//一般我们字段名都是大写的，但是我们json里面都是小写的，这里就可以通过tag来使用小写来知道大写的字段type User struct {Namestring `json:"name"`Password string `json:"password"`CreatedAt time.Time `json:"createdAt"`}func main() {u := &User{Name:"Psych",Password: "123456",CreatedAt: time.Now(),}out, err := json.MarshalIndent(u, "", "")if err != nil {log.Println(err)os.Exit(1)}fmt.Println(string(out))}
运行结果：
[Running] go run "e:\golang开发学习\go_pro\main.go"{"name": "Psych","password": "123456","createdAt": "-09-09T16:58:24.0876915+08:00"}[Done] exited with code=0 in 1.136 seconds
应用xml编码
package mainimport ("encoding/xml""fmt""os")func main() {type Address struct {City, State string}type Person struct {XMLName xml.Name `xml:"person"`Id int`xml:"id,attr"` //attr代表属性FirstName string `xml:"name>first"`LastName string `xml:"name>last"` //>代表子节点Age int`xml:"age"`Height float32 `xml:"height,omitempty"`Married boolAddressComment string `xml:"comment"`}v := &Person{Id: 13, FirstName: "Wong", LastName: "Psych", Age: 18}ment = "注释."v.Address = Address{"四川", "成都"}output, err := xml.MarshalIndent(v, "", "")if err != nil {fmt.Printf("error:%v\n", err)}_, err = os.Stdout.Write(output)if err != nil {return}}
运行结果：
[Running] go run "e:\golang开发学习\go_pro\main.go"<person id="13"><name><first>Wong</first><last>Psych</last></name><age>18</age><Married>false</Married><City>四川</City><State>成都</State><comment>注释.</comment></person>[Done] exited with code=0 in 1.248 seconds
应用form表单绑定
可以写多个tag标签，使用空格分开
type Channel struct {Iduint64 `form:"id" gorm:"primaryKey"`Title string `form:"title" gorm:"title"`Slug string `form:"slug" gorm:"slug"`Content string `form:"content" gorm:"content"`Status int `form:"status" gorm:"status"`Weight int `form:"weight" gorm:"weight"`}
gin框架form和数据绑定
package mainimport "C"import ("/gin-gonic/gin""net/http")type Login struct {//form：表单中的name一般是小写的id，json：前后端分离返回给前端的参数，binding：字段校验Userstring `form:"user" json:"user" binding:"required"`Password string `form:"password" json:"password" binding:"required"`}func main() {router := gin.Default()// 绑定 JSON ({"user":"manu","password":"123"})router.POST("/loginJSON", func(c *gin.Context) {var json Loginif err := c.ShouldBindJSON(&json); err == nil {if json.User == "manu" && json.Password == "123" {c.JSON(http.StatusOK, gin.H{"status": "成功登录"})} else {c.JSON(http.StatusUnauthorized, gin.H{"status": "未授权"})}} else {C.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})}})//HTML form (user=manu&password=123)router.POST("/loginForm", func(c *gin.Context) {var form Loginif err := c.ShouldBind(&form); err == nil {if form.User == "manu" && form.Password == "123" {c.JSON(http.StatusOK, gin.H{"status": "成功登录"})} else {c.JSON(http.StatusUnauthorized, gin.H{"status": "未授权"})}} else {C.JSON(http.StatusBadRequest, gin.H{"error": err.Error})}})}
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