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//Updateupdateattributeswithcallbacks,refer:https://jinz...

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。