gorm update传入struct对象,零值字段不更新的解决方案

使用gorm的update接口，出现如果字段为零值

则不会生成字段的更新语句

// Update update attributes with callbacks, refer: https://jinzhu.github.io/gorm/crud.html#update
// WARNING when update with struct, GORM will not update fields that with zero value
func (s *DB) Update(attrs ...interface{}) *DB {
 return s.Updates(toSearchableMap(attrs...), true)
}

如：

type AA struct {
 ID             int       `gorm:"primary_key" json:" - "`            //主键id
    Code1       string
 Code2     string
}

如果

a :=AA{
    ID:1,
    Code1:1,
    Code2:0
}

则产生的SQL语句将不包含Code2更新语句，

update aa set Code1 =1 where id =1;

出现该问题的原因在于，使用stuct类型对象作为参数时，struct会首先转化为map对象，然后再生成SQL语句，但是转化为map的过程中，对于零值字段是忽略的

// assignUpdatingAttributesCallback assign updating attributes to model
func assignUpdatingAttributesCallback(scope *Scope) {
	if attrs, ok := scope.InstanceGet("gorm:update_interface"); ok {
		if updateMaps, hasUpdate := scope.updatedAttrsWithValues(attrs); hasUpdate {
			scope.InstanceSet("gorm:update_attrs", updateMaps)
		} else {
			scope.SkipLeft()
		}
	}
}
func (scope *Scope) updatedAttrsWithValues(value interface{}) (results map[string]interface{}, hasUpdate bool) {
	if scope.IndirectValue().Kind() != reflect.Struct {
		return convertInterfaceToMap(value, false, scope.db), true
	}

	results = map[string]interface{}{}

	for key, value := range convertInterfaceToMap(value, true, scope.db) {
		if field, ok := scope.FieldByName(key); ok && scope.changeableField(field) {
			if _, ok := value.(*SqlExpr); ok {
				hasUpdate = true
				results[field.DBName] = value
			} else {
				err := field.Set(value)
				if field.IsNormal && !field.IsIgnored {
					hasUpdate = true
					if err == ErrUnaddressable {
						results[field.DBName] = value
					} else {
						results[field.DBName] = field.Field.Interface()
					}
				}
			}
		}
	}
	return
}
func convertInterfaceToMap(values interface{}, withIgnoredField bool, db *DB) map[string]interface{} {
	var attrs = map[string]interface{}{}

	switch value := values.(type) {
	case map[string]interface{}:
		return value
	case []interface{}:
		for _, v := range value {
			for key, value := range convertInterfaceToMap(v, withIgnoredField, db) {
				attrs[key] = value
			}
		}
	case interface{}:
		reflectValue := reflect.ValueOf(values)

		switch reflectValue.Kind() {
		case reflect.Map:
			for _, key := range reflectValue.MapKeys() {
				attrs[ToColumnName(key.Interface().(string))] = reflectValue.MapIndex(key).Interface()
			}
		default:
			for _, field := range (&Scope{Value: values, db: db}).Fields() {
				if !field.IsBlank && (withIgnoredField || !field.IsIgnored) {
					//只有非零值才更新
					attrs[field.DBName] = field.Field.Interface()
				}
			}
		}
	}
	return attrs
}

为了更新零值字段，则需要修改gorm库，我们这里添加一个FORCE标识字段必须更新

type AA struct {
 ID             int       `gorm:"primary_key" json:" - "`            //主键id
    Code1       string    `gorm:"force"`
 Code2     string    `gorm:"force"`
}

修改Sope的Fields函数，对于有FORCE标签的字段，IsBlank直接设置为fasle

// Fields get value's fields
//通过反射获取field的值
func (scope *Scope) Fields() []*Field {
	if scope.fields == nil {
		var (
			fields             []*Field
			indirectScopeValue = scope.IndirectValue()
			isStruct           = indirectScopeValue.Kind() == reflect.Struct
		)
		// 解析结构体
		for _, structField := range scope.GetModelStruct().StructFields {
			if isStruct {
				fieldValue := indirectScopeValue
				// 一般只有一个字段名吧？？？？？
				for _, name := range structField.Names {
					if fieldValue.Kind() == reflect.Ptr && fieldValue.IsNil() {
						// 处理数组
						fieldValue.Set(reflect.New(fieldValue.Type().Elem()))
					}
					//
					fieldValue = reflect.Indirect(fieldValue).FieldByName(name)
				}

				//有force代表强制更新
				_, ok := structField.TagSettingsGet("FORCE")
				fields = append(fields, &Field{StructField: structField, Field: fieldValue, IsBlank: isBlank(fieldValue) && !ok})
				//如果不是struct，则返回空，因为原生没有字段这个说法
			} else {
				fields = append(fields, &Field{StructField: structField, IsBlank: true})
			}
		}
		scope.fields = &fields
	}
	return *scope.fields
}

补充：Gorm 自动update操作自动过滤0和 “ “

gorm会自动过滤结构体的0 和" "

type CrmUserTableColumns struct {
	Id                        int64  `gorm:"column:ids"`
	Name                      string `gorm:"column:xxx"`
	Account                   string `gorm:"column:xxx"`
	Password                  string `gorm:"column:xxx"`
	State                     int64  `gorm:"column:state"`
	BusinessId                int64  `gorm:"column:business_id"`
	DepartmentId              int64  `gorm:"column:department_id"`
	...
}
func (u *CrmUserTableColumns) TableName() string {
	return "crm_user"
}
field := map[string]interface{}{
		"business_id":   data.BusinessId,
		"state":         data.State,
		"department_id": data.DepartmentId,
	}
	whereSql = "account = ?"
updates := dbMasterClient.
		//Debug().
		Model(&CrmUserTableColumns{}).
		Where(whereSql, whereCase).
		Updates(field)
	RowsAffected = updates.RowsAffected
	return

以上为个人经验，希望能给大家一个参考，也希望大家多多支持我们。如有错误或未考虑完全的地方，望不吝赐教。