如何最好地將 JSON 資料規範化為 Go 中的 API 結構體

php小編西瓜在這裡帶來了一個關於如何將JSON資料規範化為Go中的API結構體的精簡指南。在現代Web應用程式中，與JSON資料打交道是常見的任務。 Go語言作為一門強大的後端語言，提供了一種簡潔而靈活的方式來處理JSON資料。本文將介紹如何使用Go語言中的結構體來規範化JSON數據，從而更好地處理和操作它們。無論你是初學者還是有經驗的開發人員，本文都將為你提供有用的技巧和實用的範例。讓我們開始吧！

問題內容

我對 go 還很陌生，正在嘗試確定是否有更簡潔的方法來完成從前端 (js) 到我的 api 的 json 資料的規範化。為了確保在從結構 (model.expense) 建立變數時使用正確的類型，我將有效負載轉儲到映射中，然後標準化並保存回結構。如果有人可以教我更好的方法來處理這個問題，我將不勝感激！先致謝！

模型.費用結構：

type expense struct {
    id        primitive.objectid   `json:"_id,omitempty" bson:"_id,omitempty"`
    name      string               `json:"name"`
    frequency int                  `json:"frequency"`
    startdate *time.time           `json:"startdate"`
    enddate   *time.time           `json:"enddate,omitempty"`
    cost      primitive.decimal128 `json:"cost"`
    paid      []string             `json:"paid,omitempty"`
}

有問題的控制器：

func InsertOneExpense(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    w.Header().Set("Allow-Control-Allow-Methods", "POST")

    var expense map[string]interface{}
    json.NewDecoder(r.Body).Decode(&expense)

    var expenseName string
    if name, ok := expense["name"]; ok {
        expenseName = fmt.Sprintf("%v", name)
    } else {
        json.NewEncoder(w).Encode("missing required name")
    }

    var expenseFrequency int
    if frequency, ok := expense["frequency"]; ok {
        expenseFrequency = int(frequency.(float64))
    } else {
        expenseFrequency = 1
    }

    // Handle startDate normalization
    var expenseStartDate *time.Time
    if startDate, ok := expense["startDate"]; ok {
        startDateString := fmt.Sprintf("%v", startDate)
        startDateParsed, err := time.Parse("2006-01-02 15:04:05", startDateString)

        if err != nil {
            log.Fatal(err)
        }

        expenseStartDate = &startDateParsed
    } else {
        json.NewEncoder(w).Encode("missing required startDate")
    }

    // Handle endDate normalization
    var expenseEndDate *time.Time
    if endDate, ok := expense["endDate"]; ok {
        endDateString := fmt.Sprintf("%v", endDate)
        endDateParsed, err := time.Parse("2006-01-02 15:04:05", endDateString)

        if err != nil {
            log.Fatal(err)
        }

        expenseEndDate = &endDateParsed
    } else {
        expenseEndDate = nil
    }

    // Handle cost normaliztion
    var expenseCost primitive.Decimal128
    if cost, ok := expense["cost"]; ok {
        costString := fmt.Sprintf("%v", cost)
        costPrimitive, err := primitive.ParseDecimal128(costString)

        if err != nil {
            log.Fatal(err)
        }

        expenseCost = costPrimitive
    } else {
        json.NewEncoder(w).Encode("missing required cost")
        return
    }

    normalizedExpense := model.Expense{
        Name:      expenseName,
        Frequency: expenseFrequency,
        StartDate: expenseStartDate,
        EndDate:   expenseEndDate,
        Cost:      expenseCost,
    }

    // Do more things with the struct var...
}

解決方法

您可以定義 json.unmarshaljson 接口，然後根據需要手動驗證資料。嘗試這樣的事情：

package main

import (
    "encoding/json"
    "fmt"
    "strconv"
)

type CoolStruct struct {
    MoneyOwed string `json:"money_owed"`
}

// UnmarshalJSON the json package will delegate deserialization to our code if we implement the json.UnmarshalJSON interface
func (c *CoolStruct) UnmarshalJSON(data []byte) error {
    // get the body as a map[string]*[]byte
    raw := map[string]*json.RawMessage{}
    if err := json.Unmarshal(data, &raw); err != nil {
        return fmt.Errorf("unable to unmarshal raw meessage map: %w", err)
    }

    // if we don't know the variable type sent we can unmarshal to an interface
    var tempHolder interface{}
    err := json.Unmarshal(*raw["money_owed"], &tempHolder)
    if err != nil {
        return fmt.Errorf("unable to unmarshal custom value from raw message map: %w", err)
    }

    // the unmarshalled interface has an underlying type use go's typing
    // system to determine type conversions / normalizations required
    switch tempHolder.(type) {
    case int64:
        // once we determine the type of the we just assign the value
        // to the receiver's field
        c.MoneyOwed = strconv.FormatInt(tempHolder.(int64), 10)
    // we could list all individually or as a group; driven by requirements
    case int, int32, float32, float64:
        c.MoneyOwed = fmt.Sprint(tempHolder)
    case string:
        c.MoneyOwed = tempHolder.(string)
    default:
        fmt.Printf("missing type case: %T\n", tempHolder)
    }
    // success; struct is now populated
    return nil
}

func main() {
    myJson := []byte(`{"money_owed": 123.12}`)
    cool := CoolStruct{}
    // outside of your struct you marshal/unmarshal as normal
    if err := json.Unmarshal(myJson, &cool); err != nil {
        panic(err)
    }
    fmt.Printf("%+v\n", cool)
}

輸出：{moneyowed:123.12}
遊樂場連結：https://www.php.cn/link/87ca4eb840b6f78e3b6d6b418c0fef40

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