由于响应结构的微小变化，重复调用 JSON 解码器

Question

我已将 Github 和 Google 身份验证系统添加到我的 Web 应用程序。在这两种情况下，我都希望收到用户电子邮件。我试图制作一个函数，它会发出 API 请求并收到电子邮件。
当 Google 返回一个 JSON 对象 和 Github 一个 JSON 时，我运行遇到了一个问题array 作为响应。
我想不出一种方法可以避免两次调用 JSON 解码器，因为我不能为它们使用相同的类型变量。

// Sends a request to the API and
// authorizes it by setting HTTP header "Authorization" to authHeader value
func getUserEmail(endpoint, authHeader, provider string) (string, error) {
    var email string       // Store user email here
    var client http.Client // Create client so we can modify request headers

    // Create a GET request to the endpoint
    req, err := http.NewRequest("GET", endpoint, nil)
    if err != nil {
        return "", err
    }

    // Authorize the request by using the HTTP header
    req.Header.Add("Authorization", authHeader)

    // Give the data back as JSON
    req.Header.Add("accept", "application/json")

    // Send the request
    resp, err := client.Do(req)
    if err != nil {
        fmt.Println("Internet connection or client policy error")
        return "", err
    }
    defer resp.Body.Close()

    if provider == "google" {
        var response map[string]interface{}

        err = json.NewDecoder(resp.Body).Decode(&response)
        if err != nil {
            fmt.Println("Error occured during decoding access token response")
            return "", err
        }

        email = response["email"].(string)

    } else if provider == "github" {
        var response []map[string]interface{}

        err = json.NewDecoder(resp.Body).Decode(&response)
        if err != nil {
            fmt.Println("Error occured during decoding access token response")
            return "", err
        }

        email = response[0]["email"].(string)
    } else {
        return "", errors.New("invalid provider")

    }

    return email, nil
}

Answer 1

您可以解组为 var response interface{}。一旦 json 被解组，您可以在 response 上执行 type assertion 以检查它是 []interface{} 还是 map[string]interface{} 并从那里开始。

var email string
var response interface{}
if err := json.NewDecoder(r.Body).Decode(&response); err != nil {
    return err
}

// If you are sure that the structure of the content of the response,
// given its type, is always what you expect it to be, you can use a
// quick-and-dirty type switch/assertion.
switch v := response.(type) {
case []interface{}:
    email = v[0].(map[string]interface{})["email"].(string)
case map[string]interface{}:
    email = v["email"].(string)
}

// But! If you're not sure, if the APIs don't provide a guarantee,
// then you should guard against panics using the comma-ok idiom
// at every step.
if s, ok := response.([]interface{}); ok && len(s) > 0 {
    if m, ok := s[0].(map[string]interface{}); ok && len(m) > 0 {
        email, _ = m["email"].(string)
    }
} else if m, ok := response.(map[string]interface{}); ok && len(m) > 0 {
    email, _ = m["email"].(string)
}

您还可以pre-allocate一个指针到基于提供者值的预期类型并将请求正文解组到其中，这将减少类型断言的数量必要但需要 pointer-dereferencing.

var email string
var response interface{}
if provider == "google" {
    response = new(map[string]interface{})
} else if provider == "github" {
    response = new([]map[string]interface{})
}
if err := json.NewDecoder(r.Body).Decode(response); err != nil {
    return err
}

switch v := response.(type) {
case *[]map[string]interface{}:
    email = (*v)[0]["email"].(string) // no need to assert the slice element's type
case *map[string]interface{}:
    email = (*v)["email"].(string)
}

由于响应结构的微小变化，重复调用 JSON 解码器

Calling JSON decoder repetitvely because of small change in response structure

json

http

go

oauth-2.0