for-loop - 如何在 Golang 中迭代结构中的 slice 或者是否可以在结构中使用 for 循环？

Question

我有两个结构。一种是抽奖，一种是奖励。我使用的是Mysql数据库。我想从数据库读取数据并以 JSON 格式写入。我可以做到这一点，但我想要一个嵌套结构，我想在 Lottery 结构中迭代 Reward 结构。我可以这样做吗？

这是我的彩票和奖励结构

type Lottery struct{
    Id int `json:"lottery_id"`
    Lottery string `json:"lottery_name"`
    Description string `json:"lottery_description"`
    Reward []Rew `json:"rewards"`
}

type Rew struct{
    Id int `json:"reward_id"`
    RewardName string `json:"reward_name"`
    Description string `json:"reward_description"`
    Asset int `json:"reward_asset"`
    AssetName string `json:"reward_asset_name"`
}

这是我的代码

app.Get("/lottery/{id:int}", func (ctx iris.Context){
        id1 := ctx.Params().GetIntDefault("id",0)

        stmtOut, err := db.Prepare("select lottery_name, lottery_description from lottery_table where id = ?")
        if err !=nil{
            panic(err.Error())
        }
        defer stmtOut.Close()

        var lottery_name, lottery_description string

        err1 := stmtOut.QueryRow(id1).Scan(&lottery_name,&lottery_description)
        if err != nil{
            panic(err1.Error())
        }

        stmtOut1, err := db.Query("select id, reward_name, reward_description, reward_asset, reward_asset_name from rewards_table where lottery_id = ?",id1)
        if err != nil{
            panic(err.Error())
        }
        defer stmtOut1.Close()

        for stmtOut1.Next() {

            var id, reward_asset int
            var reward_name, reward_description, reward_asset_name string

            err2 := stmtOut1.Scan(&id, &reward_name, &reward_description, &reward_asset, &reward_asset_name)
            if err2 != nil {
                panic(err.Error())
            }

                rew := Lottery{
                Id:          id1,
                Lottery:     lottery_name,
                Description: lottery_description,
                Reward : []Rew{Rew{
                    Id:          id,
                    RewardName:  reward_name,
                    Description: reward_description,
                    Asset:       reward_asset,
                    AssetName:   reward_asset_name,
                },
                },
            }

            ctx.JSON(&rew)
        }


    })

当我使用上述函数时，我得到这样的 JSON 格式

{
    "lottery_id": 7,
    "lottery_name": "lottery2",
    "lottery_description": "lottery for 7",
    "rewards": [
        {
            "reward_id": 9,
            "reward_name": "Reward3",
            "reward_description": "Reward for lottery 7",
            "reward_asset": 20,
            "reward_asset_name": "AC"
        }
    ]
}{
    "lottery_id": 7,
    "lottery_name": "lottery2",
    "lottery_description": "lottery for 7",
    "rewards": [
        {
            "reward_id": 10,
            "reward_name": "Reward5",
            "reward_description": "Reward for lottery 7",
            "reward_asset": 15,
            "reward_asset_name": "AC"
        }
    ]
}

但是我想将 JSON 获取为

{
"lottery_id":7,
"lottery_name":"lottery2"
"lottery_description":"lottery for 7"
"rewards":[
    {
        "reward_id":9,
        "reward_name": "Reward3",
        "reward_description": "Reward for lottery 7",
        "reward_asset": 20,
        "reward_asset_name": "ABC"
    },
    {   "reward_id":10,
        "reward_name": "Reward5",
        "reward_description": "Reward for lottery 7",
        "reward_asset": 15,
        "reward_asset_name": "ABC"
    },
    {   "reward_id":11,
        "reward_name": "Reward7",
        "reward_description": "Reward for lottery 7",
        "reward_asset": 10,
        "reward_asset_name": "ABC"
    }
    ]
}

如何在结构体中进行迭代？结构体中是否可以有 for 循环？或者还有其他方法可以获取上面的 JSON 吗？

请帮助我。

Answer 1

类似这样的事情:

app.Get("/lottery/{id:int}", func(ctx iris.Context) {
    id1 := ctx.Params().GetIntDefault("id", 0)

    stmtOut, err := db.Prepare("select lottery_name, lottery_description from lottery_table where id = ?")
    if err != nil {
        panic(err.Error())
    }
    defer stmtOut.Close()

    lot := Lottery{Id: id1}
    err1 := stmtOut.QueryRow(id1).Scan(&lot.Lottery, &lot.Description)
    if err != nil {
        panic(err1.Error())
    }

    stmtOut1, err := db.Query("select id, reward_name, reward_description, reward_asset, reward_asset_name from rewards_table where lottery_id = ?", id1)
    if err != nil {
        panic(err.Error())
    }
    defer stmtOut1.Close()

    for stmtOut1.Next() {
        rew := Rew{}
        err2 := stmtOut1.Scan(&rew.Id, &rew.RewardName, &rew.Description, &rew.Asset, &rew.AssetName)
        if err2 != nil {
            panic(err.Error())
        }
        lot.Reward = append(lot.Reward, rew)

    }
    ctx.JSON(lot)
})