Your Question

gorm有preload的方法，但是有的时候，我已经获取到了model或者model数组，想要加载其中的某个关联字段

比如

type Answer struct {
    ID         int64          `gorm:"column:id;primaryKey"`
    QuestionID int64          `gorm:"column:question_id;index;comment:问题id;not null;default 0"`
    Context    string         `gorm:"column:context;comment:内容"`
    AuthorID   int64          `gorm:"column:author_id;comment:作者id;not null;default:0"`
    CreatedAt  time.Time      `gorm:"column:created_at;autoCreateTime;comment:创建时间"`
    UpdatedAt  time.Time      `gorm:"column:updated_at;autoUpdateTime;autoCreateTime;<-:false;comment:更新时间"`
    DeletedAt  gorm.DeletedAt `gorm:"index"`
    Author     *user.User     `gorm:"foreignKey:ID;references:author_id"`
    Question   *Question      `gorm:"foreignKey:QuestionID"`
}

我已经获取到了as := []Answers，之后我想要加载Author字段，目前我只能使用

if err := q.ormDB.WithContext(ctx).Preload("Author").Order("created_at desc").Find(answers, ids).Error; err != nil {
        return err
    }

但是这个会增加一次

{"begin":"2021-12-05T18:24:38.063506+08:00","error":null,"level":7,"msg":"orm trace sql","rows":6,"sql":"SELECT * FROM `answers` WHERE `answers`.`id` IN (25,24,23,22,21,20) AND `answers`.`deleted_at` IS NULL ORDER BY created_at desc","time":1234329,"timestamp":"2021-12-05T18:24:38+08:00"}

有没有办法有PostLoad之类的请求？还是我的使用有什么问题？

The document you expected this should be explained

Expected answer

Comment From: ghost

https://gorm.cn/zh_CN/docs/preload.html#%E8%87%AA%E5%AE%9A%E4%B9%89%E9%A2%84%E5%8A%A0%E8%BD%BD-SQL

Comment From: jianfengye

这个还是preload，比如

// AnswersLoadAuthor 批量加载Author字段
func (q *QaService) AnswersLoadAuthor(ctx context.Context, answers *[]*Answer) error {
    if answers == nil {
        return nil
    }
    answerColl := collection.NewObjPointCollection(*answers)
    ids, err := answerColl.Pluck("ID").ToInt64s()
    if err != nil {
        return err
    }
    if len(ids) == 0 {
        return nil
    }
    q.logger.Debug(ctx, "ids", map[string]interface{}{
        "ids": ids,
    })

    if err := q.ormDB.WithContext(ctx).Preload("Author").Order("created_at desc").Find(answers, ids).Error; err != nil {
        return err
    }
    return nil
}

这个函数，参数已经传递了answers了，我只是要填充answers中的Author字段，但是这个sql语句会有两个语句：

select * from answers where id in (1,2,3)
select * from users where id in (11,12,13)

但是里面的第一个sql语句其实我是不想要的，所以我想，已经有了一个ansewers数组了，能不能有一个postload，能只加载Author，就是加载第二个sql语句？

Comment From: ghost

自定义预加载 的SQL 试试呢～

Comment From: jianfengye

自定义预加载 的SQL 试试呢～

能再说的详细一些么？我理解预加载的sql是做不到的

Comment From: ghost

自定义预加载 的SQL 试试呢～

能再说的详细一些么？我理解预加载的sql是做不到的

抱歉,我理解错了,这的确不行。:zipper_mouth_face:

Comment From: github-actions[bot]

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Comment From: jinzhu

Maybe we can add a Load function to the Association Mode

Comment From: qeq66

@jinzhu 什么时候可以安排上，急需这个方法