GORM

该笔记使用的gorm是对应的v2版本的gorm ，如果是使用的v1版本可能会有很大的区别，特此提醒；

快速开始

go get gorm.io/gorm
go get gorm.io/driver/mysql

package main

import (
	"fmt"
	huge "github.com/dablelv/go-huge-util"
	"gorm.io/driver/mysql"
	"gorm.io/gorm"
	"log"
)

type Ziop struct {
	gorm.Model
	Name string
	Age  int
	Like string
}

func (z *Ziop) TableName() string { return "grid_ziop" }
func main() {
	dataSource := "ziop:ziop@/demo?charset=utf8mb4&parseTime=True&loc=Local"
	db, err := gorm.Open(mysql.Open(dataSource), &gorm.Config{})
	if err != nil {
		log.Fatal(err, "数据库连接失败")
	}
    err = db.AutoMigrate(&Ziop{})
	if err != nil {
		log.Fatal(err)
	}

	// 新增
	ziop := Ziop{
		Name: "ziop",
		Age:  21,
		Like: "codings",
	}
	db.Create(&ziop)

	//查询
	var z []Ziop
	ziopDb := db.Model(&Ziop{})
	ziopDb.Where("Age > ?", 23).Find(&z)

	//修改
	ziopDb.Where("id in (?)", []int{1, 2, 3}).Updates(Ziop{
		Name: "Ziop",
	}).First(&z)

	// 软删除
	ziopDb.Delete("id = ?", 1)
	// 硬删除
	ziopDb.Unscoped().Delete("id = ?", 1)
	// 打印
	json, err := huge.ToIndentJSON(&z)
	fmt.Printf("Ziop = %+v", json)
}

V2特性

Update Hook 支持 Changed

当使用 Update，Updates 更新时，您可以在 BeforeUpdate, BeforeSave Hook 中使用 Changed 方法来检查字段是否有更改.

func (user *User) BeforeUpdate(tx *gorm.DB) error {
  if tx.Statement.Changed("Name", "Admin") { // if Name or Admin changed
    tx.Statement.SetColumn("Age", 18)
  }

  if tx.Statement.Changed() { // 如果任何字段有变动
    tx.Statement.SetColumn("Age", 18)
  }
  return nil
}
// update field `Name` to `Jinzhu`
db.Model(&user).Update("Name", "Jinzhu") 

// update field `Name` to `Jinzhu`, `Admin` to false
db.Model(&user).Updates(map[string]interface{}{"name": "Jinzhu", "admin": false})

// Update none zero fields when using struct as argument, will only update `Name` to `Jinzhu`
db.Model(&user).Updates(User{Name: "Jinzhu", Admin: false}) 

// update selected fields `Name`, `Admin`，`Admin` will be updated to zero value (false)
db.Model(&user).Select("Name", "Admin").Updates(User{Name: "Jinzhu"}) 

// update selected fields exists in the map, will only update field `Name` to `Jinzhu`
db.Model(&user).Select("Name", "Admin").Updates(map[string]interface{}{"Name": "Jinzhu"}) 


// Attention: `Changed` will only check the field value of `Update` / `Updates` equals `Model`'s field value, it returns true if not equal and the field will be saved

// Changed("Name") => true
db.Model(&User{ID: 1, Name: "jinzhu"}).Updates(map[string]interface{"name": "jinzhu2"}) 
 
// Changed("Name") => false, `Name` not changed
db.Model(&User{ID: 1, Name: "jinzhu"}).Updates(map[string]interface{"name": "jinzhu"})

// Changed("Name") => false, `Name` not selected to update
db.Model(&User{ID: 1, Name: "jinzhu"}).Select("Admin").Updates(map[string]interface{"name": "jinzhu2", "admin": false}) 

// Changed("Name") => true
db.Model(&User{ID: 1, Name: "jinzhu"}).Updates(User{Name: "jinzhu2"}) 

 // Changed("Name") => false, `Name` not changed
db.Model(&User{ID: 1, Name: "jinzhu"}).Updates(User{Name: "jinzhu"}) 

// Changed("Name") => false, `Name` not selected to update
db.Model(&User{ID: 1, Name: "jinzhu"}).Select("Admin").Updates(User{Name: "jinzhu2"})