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Version: 2.8.x(Latest)

Avoid Object Initialization and sql.ErrNoRows Judgment in Queries​

When executing SQL queries, avoid initializing query results in advance to prevent the influence of default values in the struct objects and unnecessary object memory creation. By judging a return object pointer as nil, avoid using sql.ErrNoRows, thereby reducing the code's complexity in handling error and unifying the project’s logic for handling empty query results.

A counterexample:

func (s *sTask) GetOne(ctx context.Context, id uint64) (out *entity.ResourceTask, err error) {
    out = new(model.TaskDetail)
    err = dao.ResourceTask.Ctx(ctx).WherePri(id).Scan(out)
    if err != nil {
        if err == sql.ErrNoRows {
            err = gerror.Newf(`record not found for "%d"`, id)
        }
        return
    }
    return
}

In this example, the returned out object actually has default values due to object initialization (regardless of whether the SQL query retrieves data), and the judgment of sql.ErrNoRows adds complexity to error handling logic in the code.

Recommended improvement:

func (s *sTask) GetOne(ctx context.Context, id uint64) (out *entity.ResourceTask, err error) {
    err = dao.ResourceTask.Ctx(ctx).WherePri(id).Scan(&out)
    if err != nil {
        return
    }
    if out == nil {
        err = gerror.Newf(`record not found for "%d"`, id)
    }
    return
}
warning

Note the use of &out in the code.

For more information, please refer to: ORM Result - Empty Check