type User struct { gorm.Model Username string Orders []Order}type Order struct { gorm.Model UserID uint Price float64}// 预加载 Order 数据,参数二可以传递一个 func(db gorm.PreloadBuilder) error 闭包函数,里边拼接查询条件、排序方式等.Preload("Order", nil)// 条件预加载.Preload("Orders", "state NOT IN (?)", "cancelled")// 嵌套.Preload("Orders.OrderItems.Product")