如何解组数组内的对象

huangapple
go评论116阅读模式
英文:

How to unmarshal objects inside array

问题

我正在尝试访问数组中对象的值。

  1. [
  2.   {
  3.     "name": "London",
  4.     "lat": 51.5073219,
  5.     "lon": -0.1276474,
  6.     "country": "GB",
  7.     "state": "England"
  8.   }
  9. ]

我使用以下代码进行解组：

  1. content, err := ioutil.ReadAll(res.Body)
  2. if err != nil {
  3.     log.Fatal(err)
  4. }
  6. var data []ResponseData
  7. err = json.Unmarshal(content, &data)
  8. if err != nil {
  9.     log.Fatal(err)
  10. }

这是我的结构体：

  1. type ResponseData struct {
  2.     Name    string  `json:"name"`
  3.     Lat     float32 `json:"lat"`
  4.     Lon     float32 `json:"lon"`
  5.     Country string  `json:"country"`
  6.     State   string  `json:"state"`
  7. }

稍后，我只需要使用fmt.Println(data.Lat, data.Lon)即可。

英文:

I am trying to get access to object's values inside of array

  1. [
  2.   {
  3.     "name": "London",
  4.     "lat": 51.5073219,
  5.     "lon": -0.1276474,
  6.     "country": "GB",
  7.     "state": "England"
  8.   }
  9. ]

I use this code to unmarshal it

  1. content, err := ioutil.ReadAll(res.Body)
  2. 	if err != nil {
  3. 		log.Fatal(err)
  4. 	}
  6. 	var data []ResponseData
  7. 	err = json.Unmarshal(content, &data)
  8. 	if err != nil {
  9. 		log.Fatal(err)
  10. 	}

This is my struct

  1. type ResponseData struct {
  2. 	Name       string      `json:"name"`
  3. 	Lat        float32     `json:"lat"`
  4. 	Lon        float32     `json:"lon"`
  5. 	Country    string      `json:"country"`
  6. 	State      string      `json:"state"`
  7. }

I need to simply fmt.Println(data.Lat, data.Lon) later.

答案1

得分: 1

你提供的代码应该可以成功解析JSON；问题出在你尝试使用结果的方式上。你说你想使用fmt.Println(data.Lat, data.Lon)，但这样是行不通的，因为data是一个切片（[]ResponseData），而不是ResponseData。你可以使用fmt.Println(data[0].Lat, data[0].Lon)（在检查元素数量后！），或者遍历元素。

下面的代码可能对你的实验有所帮助（playground - 这里包含比下面更多的内容）：

  1. package main
  3. import (
  4. 	"encoding/json"
  5. 	"fmt"
  6. 	"log"
  7. )
  9. const rawJSON = `[
  10.   {
  11.     "name": "London",
  12.     "lat": 51.5073219,
  13.     "lon": -0.1276474,
  14.     "country": "GB",
  15.     "state": "England"
  16.   }
  17. ]`
  19. type ResponseData struct {
  20. 	Name    string  `json:"name"`
  21. 	Lat     float32 `json:"lat"`
  22. 	Lon     float32 `json:"lon"`
  23. 	Country string  `json:"country"`
  24. 	State   string  `json:"state"`
  25. }
  27. func main() {
  28. 	var data []ResponseData
  29. 	err := json.Unmarshal([]byte(rawJSON), &data)
  30. 	if err != nil {
  31. 		log.Fatal(err)
  32. 	}
  34. 	if len(data) == 1 { // Would also work for 2+ but then you are throwing data away...
  35. 		fmt.Println("test1", data[0].Lat, data[0].Lon)
  36. 	}
  38. 	for _, e := range data {
  39. 		fmt.Println("test2", e.Lat, e.Lon)
  40. 	}
  41. }
英文:

The code you presented should unmarshal your JSON successfully; the issue is with the way you are trying to use the result. You say you want to use fmt.Println(data.Lat, data.Lon) but this will not work because data is a slice ([]ResponseData) not a ResponseData. You could use fmt.Println(data[0].Lat, data[0].Lon) (after checking the number of elements!) or iterate through the elements.

The below might help you experiment (playground - this contains a little more content than below):

  1. package main
  3. import (
  4. 	"encoding/json"
  5. 	"fmt"
  6. 	"log"
  7. )
  9. const rawJSON = `[
  10.   {
  11.     "name": "London",
  12.     "lat": 51.5073219,
  13.     "lon": -0.1276474,
  14.     "country": "GB",
  15.     "state": "England"
  16.   }
  17. ]`
  19. type ResponseData struct {
  20. 	Name    string  `json:"name"`
  21. 	Lat     float32 `json:"lat"`
  22. 	Lon     float32 `json:"lon"`
  23. 	Country string  `json:"country"`
  24. 	State   string  `json:"state"`
  25. }
  27. func main() {
  28. 	var data []ResponseData
  29. 	err := json.Unmarshal([]byte(rawJSON), &data)
  30. 	if err != nil {
  31. 		log.Fatal(err)
  32. 	}
  34. 	if len(data) == 1 { // Would also work for 2+ but then you are throwing data away...
  35. 		fmt.Println("test1", data[0].Lat, data[0].Lon)
  36. 	}
  38. 	for _, e := range data {
  39. 		fmt.Println("test2", e.Lat, e.Lon)
  40. 	}
  41. }

huangapple
  • 本文由 发表于 2022年8月6日 07:49:54
  • 转载请务必保留本文链接：https://go.coder-hub.com/73256220.html
  • arrays
  • go
  • json
  • object
  • unmarshalling
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