如何从 map[string]interface{} 中提取数据？

huangapple
go评论137阅读模式
英文:

How to extract data from map[string]interface{}?

问题

我正在将数据发送到API，如下所示：

  1. {"after": {"amount": 811,"id":123,"status":"Hi"}, "key": [70]}

并且在打印时我得到以下结果：

  1. map[after:map[amount:811 id:123 status:Hi ] key:[70]]

有没有办法像这样打印单个字段呢？
amount::800
id:123
status:Hi

代码如下：

  1. package main
  3. import (
  4. 	"encoding/json"
  5. 	"fmt"
  6. 	"io"
  7. 	"io/ioutil"
  8. 	"log"
  9. 	"net/http"
  10. 	"strings"
  11. )
  13. var (
  14. 	PORT = ":8080"
  15. )
  17. func main() {
  18. 	fmt.Println("In Main")
  19. 	http.HandleFunc("/", changedData)
  20. 	http.ListenAndServe(PORT, nil)
  21. }
  23. type Data struct {
  24. 	Id     int64   `json:"id"`
  25. 	Amount float64 `json:"amount"`
  26. 	Status string  `json:"status"`
  27. }
  29. type mark map[string]interface{}
  31. func changedData(w http.ResponseWriter, r *http.Request) {
  32. 	fmt.Println("Coming From API")
  34. 	reqBody, _ := ioutil.ReadAll(r.Body)
  35. 	fmt.Println("Data coming from API ", string(reqBody))
  37. 	digit := json.NewDecoder(strings.NewReader(string(reqBody)))
  39. 	for digit.More() {
  40. 		var result mark
  41. 		err := digit.Decode(&result)
  42. 		if err != nil {
  43. 			if err != io.EOF {
  44. 				log.Fatal(err)
  45. 			}
  46. 			break
  47. 		}
  48. 		fmt.Println("final_data ", result)
  49. 	}
  50. }
英文:

I am sending the data to the API like following:

  1. {"after": {"amount": 811,"id":123,"status":"Hi"}, "key": [70]}

and i am getting following while printing :

  1.  map[after:map[amount:811 id:123 status:Hi ] key:[70]]

Is there any way to print individual field like this??
amount::800
id:123
status:Hi

The code:

  1. package main
  3. import (
  4. 	"encoding/json"
  5. 	"fmt"
  6. 	"io"
  7. 	"io/ioutil"
  8. 	"log"
  9. 	"net/http"
  10. 	"strings"
  11. )
  13. var (
  14. 	PORT       = ":8080"
  15. )
  17. func main() {
  18. 	fmt.Println("In Main")
  19. 	http.HandleFunc("/", changedData)
  20. 	http.ListenAndServe(PORT, nil)
  21. }
  23. type Data struct {
  24. 	Id               int64 `json:"id"`
  25. 	Amount           float64 `json:"amount"`
  26. 	Status           string  `json:"status"`
  27. 	
  28. }
  31. type mark map[string]interface{}
  33. func changedData(w http.ResponseWriter, r *http.Request) {
  34. 	fmt.Println("Coming From API")
  35. 	
  36. 	reqBody, _ := ioutil.ReadAll(r.Body)
  37. 	fmt.Println("Data coming from API ", string(reqBody))
  39. 	digit := json.NewDecoder(strings.NewReader(string(reqBody)))
  41. 	for digit.More() {
  42. 		var result mark
  43. 		err := digit.Decode(&result)
  44. 		if err != nil {
  45. 			if err != io.EOF {
  46. 				log.Fatal(err)
  47. 			}
  48. 			break
  49. 		}
  50. 		fmt.Println("final_data ", result)
  51. }
  52. }

答案1

得分: 2

将其解码为与JSON文档结构匹配的Go类型。您为“after”字段声明了一个类型。将该类型与一个结构体包装以匹配文档。

  1. func changedData(w http.ResponseWriter, r *http.Request) {
  2.     var v struct{ After Data }
  3.     err := json.NewDecoder(r.Body).Decode(&v)
  4.     if err != nil {
  5.         http.Error(w, "bad request", 400)
  6.         return
  7.     }
  8.     fmt.Printf("final_data: %#v", v.After)
  9. }

Playground示例。

英文:

Decode to a Go type that matches the structure of the JSON document. You declared a type for the "after" field. Wrap that type with a struct to match the document.

  1. func changedData(w http.ResponseWriter, r *http.Request) {
  2. 	var v struct{ After Data }
  3. 	err := json.NewDecoder(r.Body).Decode(&v)
  4. 	if err != nil {
  5. 		http.Error(w, "bad request", 400)
  6. 		return
  7. 	}
  8. 	fmt.Printf("final_data: %#v", v.After)
  9. }

Playground example.

答案2

得分: 1

我认为如果你了解JSON文件的格式，或者JSON格式是预定义的，你可以定义一个struct类型。据我所知，当你不知道JSON格式或者没有预定义的格式时，大多数情况下使用interface{}是一种方法。如果你定义了一个struct类型并在将JSON解组为结构体时使用它，你可以通过像data.Id或data.Status这样的方式访问变量。

这是一个示例代码：

  1. package main
  3. import (
  4. 	"encoding/json"
  5. 	"fmt"
  6. )
  8. type Data struct {
  9. 	AfterData After `json:"after"`
  10. 	Key       []int `json:"key"`
  11. }
  13. type After struct {
  14. 	Id     int64   `json:"id"`
  15. 	Amount float64 `json:"amount"`
  16. 	Status string  `json:"status"`
  17. }
  19. func main() {
  20. 	j := []byte(`{"after": {"amount": 811,"id":123,"status":"Hi"}, "key": [70]}`)
  21. 	var data *Data
  22. 	err := json.Unmarshal(j, &data)
  23. 	if err != nil {
  24. 		fmt.Println(err.Error())
  25. 		return
  26. 	}
  27. 	fmt.Println(data.AfterData)
  28. 	fmt.Println(data.AfterData.Id)
  29. 	fmt.Println(data.AfterData.Amount)
  30. 	fmt.Println(data.AfterData.Status)
  31. }

输出将会是：

  1. {123 811 Hi}
  2. 123
  3. 811
  4. Hi

Go Playground

英文:

I think you can define a struct type if you know the JSON file format or if the JSON format is predefined. As far as I know that mostly using interface{} is a way when you don't know the JSON format or there is no predefined format of the JSON. If you define a struct type  and use it while unmarshaling the JSON to struct, you can access the variables by typing like data.Id or data.Status.

Here's an example code:

  1. package main
  3. import (
  4. 	"encoding/json"
  5. 	"fmt"
  6. )
  8. type Data struct {
  9. 	AfterData After `json:"after"`
  10. 	Key       []int `json:"key"`
  11. }
  13. type After struct {
  14. 	Id     int64   `json:"id"`
  15. 	Amount float64 `json:"amount"`
  16. 	Status string  `json:"status"`
  17. }
  19. func main() {
  20. 	j := []byte(`{"after": {"amount": 811,"id":123,"status":"Hi"}, "key": [70]}`)
  21. 	var data *Data
  22. 	err := json.Unmarshal(j, &data)
  23. 	if err != nil {
  24. 		fmt.Println(err.Error())
  25. 		return
  26. 	}
  27. 	fmt.Println(data.AfterData)
  28. 	fmt.Println(data.AfterData.Id)
  29. 	fmt.Println(data.AfterData.Amount)
  30. 	fmt.Println(data.AfterData.Status)
  32. }

Output will be

  1. {123 811 Hi}
  2. 123
  3. 811
  4. Hi

Go Playground

huangapple
  • 本文由 发表于 2021年11月14日 00:40:06
  • 转载请务必保留本文链接：https://go.coder-hub.com/69956272.html
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