json: 无法将字符串解组到 Go 结构字段中

Question

我想创建一个 CRUD rest API 来使用 Gorm 和 Gin 管理转换。当我在我的两个模型之间添加关系时，我无法创建转换，因为将字符串 ID 转换为结构类型。

我的模特：

type Cast struct {
    ID            string    `sql:"type:uuid;primary_key;default:uuid_generate_v4()"`
    FullName      string    `gorm:"size:150;not null" json:"full_name"`
    NickNames     string    `gorm:"size:250;null;" json:"nick_names"`
    BornLocation  Country   `gorm:"many2many:CastBornLocation;association_foreignkey:ID;foreignkey:ID" json:"born_location"`
    Nationalities []Country `gorm:"many2many:Castnationalities;association_foreignkey:ID;foreignkey:ID" json:"cast_nationalities"`
    MiniBio       string    `gorm:"size:1000;null;" json:"mini_bio"`
}

type Country struct {
    ID        string    `sql:"type:uuid;primary_key;default:uuid_generate_v4()"`
    Title     string    `gorm:"size:100;not null" json:"title"`
    CreatedAt time.Time `gorm:"default:CURRENT_TIMESTAMP" json:"created_at"`
    UpdatedAt time.Time `gorm:"default:CURRENT_TIMESTAMP" json:"updated_at"`
}

这是控制器：

func (server *Server) CreateCast(c *gin.Context) {
    errList = map[string]string{}
    body, err := ioutil.ReadAll(c.Request.Body)
    if err != nil {
        errList["Invalid_body"] = "Unable to get request"
        c.JSON(http.StatusUnprocessableEntity, gin.H{
            "status": http.StatusUnprocessableEntity,
            "error":  errList,
        })
        return
    }

    item := models.Cast{}
    err = json.Unmarshal(body, &item)
    if err != nil {
        fmt.Println("---------------------------------")
        fmt.Println(err)
        fmt.Println("---------------------------------")
        errList["Unmarshal_error"] = "Cannot unmarshal body"
        c.JSON(http.StatusUnprocessableEntity, gin.H{
            "status": http.StatusUnprocessableEntity,
            "error":  errList,
        })
        return
    }
    ...

这是我要提交给 API 的 JSON 正文：

{
    "full_name": "Cast fullname",
    "nick_names": "nickname1, nickname2",
    "born_location": "01346a2e-ae50-45aa-8b3e-a66748a76955",
    "Nationalities": [
        "c370aa49-b39d-4797-a096-094b84903f27",
        "01346a2e-ae50-45aa-8b3e-a66748a76955"
    ],
    "mini_bio": "this is the mini bio of the cast"
}

这是完整的打印错误：

json: cannot unmarshal string into Go struct field Cast.born_location of type models.Country

Answer 1

您不能将字符串解组为 Struct 类型。 BornLocation 是国家/地区结构类型，但您在 JSON 中发送的是字符串类型的唯一 ID。 Nationalities 也一样。尝试在对象内部的 id 节点中发送 id 以映射到您的结构。

{
    "full_name": "Cast fullname",
    "nick_names": "nickname1, nickname2",
    "born_location": {
        "id" :"01346a2e-ae50-45aa-8b3e-a66748a76955"
    }
    "Nationalities": [
        {
           "id" :"c370aa49-b39d-4797-a096-094b84903f27"
        },
        {
           "id" :"01346a2e-ae50-45aa-8b3e-a66748a76955"
        }
    ],
    "mini_bio": "this is the mini bio of the cast"
}

或者为您的请求正文创建另一个结构来映射您当前的 JSON。

json: 无法将字符串解组到 Go 结构字段中

json: cannot unmarshal string into Go struct field

go

go-gorm

go-gin