我能够通过这种情况部分解决这个问题
不幸的是，Preload() 函数似乎不适用于深入研究相关对象集。
为了澄清，我有以下模型：
type Room struct {
gorm.Model
Name string
Games []Game `gorm:"ForeignKey:RoomID"`
}
type Game struct {
gorm.Model
RoomID int `gorm:"index"`
Players []Player `gorm:"ForeignKey:GameID"`
}
type Player struct {
gorm.Model
Name string
GameID int `gorm:"index"`
}
当我创建一个包含新房间、游戏和玩家对象的新对象时，我会返回以下数据（json 编码）：
{"Value":{"ID":26,"CreatedAt":"2016-05-15T01:21:22.426234189-07:00","UpdatedAt":"2016-05-15T01:21:22.426234189-07:00","DeletedAt":null,"Name":"foo","Games":[{"ID":17,"CreatedAt":"2016-05-15T01:21:22.427026134-07:00","UpdatedAt":"2016-05-15T01:21:22.427026134-07:00","DeletedAt":null,"RoomID":26,"Turns":null,"Players":[{"ID":4,"CreatedAt":"2016-05-15T01:21:22.427560561-07:00","UpdatedAt":"2016-05-15T01:21:22.427560561-07:00","DeletedAt":null,"Name":"TestPlayer","GameID":17}],"Counter":1,"Assigned":false}],"Testing":false},"Error":null,"RowsAffected":1}
但是，如果我尝试使用 preload() 函数查询结构，我会得到以下信息：
{"Value":{"ID":26,"CreatedAt":"2016-05-15T01:21:22.426234189-07:00","UpdatedAt":"2016-05-15T01:21:22.426234189-07:00","DeletedAt":null,"Name":"foo","Games":[{"ID":17,"CreatedAt":"2016-05-15T01:21:22.427026134-07:00","UpdatedAt":"2016-05-15T01:21:22.427026134-07:00","DeletedAt":null,"RoomID":26,"Turns":null,"Players":null,"Counter":1,"Assigned":false}],"Testing":false},"Error":null,"RowsAffected":1}
请注意，Players 部分现在为空。这是我的房间注册和房间查询功能：
func RegisterRoom(w http.ResponseWriter, r *http.Request) {
err := r.ParseForm()
if err != nil {
// Handle error
}
// r.PostForm is a map of our POST form values
room := Room{
Name: r.PostFormValue("label"),
Games: []Game{{
Counter: 1,
Players: []Player{{Name: r.PostFormValue("username")}},
}},
}
t := db.Create(&room)
if err := json.NewEncoder(w).Encode(t); err != nil {
panic(err)
}
}
func RoomShow(w http.ResponseWriter, r *http.Request) {
var rm Room
vars := mux.Vars(r)
roomId := vars["roomId"]
id, _ := strconv.Atoi(roomId)
room := db.Preload("Games").First(&rm, id)
result := db.Find(&room)
json.NewEncoder(w).Encode(result)
}