英文:
Parsing JSON files with arrays in Go
问题
以下是我试图解析的JSON文件（如果有人感兴趣，这是OpenWeatherMap API）。内置的encoding/json在这方面做得相当不错。当我使用json.Unmarshal(testJson, &parsed)时，大部分JSON文件都被正确解析了。然而，由于其格式的原因，"weather"部分让我头疼。
我使用parsedMap := parsed.(map[string]interface{})解析了encoding/json生成的文件，当我尝试引用键值对中的键"main"时，它是有效的。
使用fmt.Println()，值为map[temp:280.32 pressure:1012 humidity:81 temp_min:279.15 temp_max:281.15]，我可以处理它。
然而，对于键"weather"，我得到了[map[icon:09d id:300 main:Drizzle description:light intensity drizzle]]。额外的方括号似乎引起了问题。
{
"coord": {
"lon": -0.13,
"lat": 51.51
},
"weather": [
{
"id": 300,
"main": "Drizzle",
"description": "light intensity drizzle",
"icon": "09d"
}
],
"base": "stations",
"main": {
"temp": 280.32,
"pressure": 1012,
"humidity": 81,
"temp_min": 279.15,
"temp_max": 281.15
},
"visibility": 10000,
"wind": {
"speed": 4.1,
"deg": 80
},
"clouds": {
"all": 90
},
"dt": 1485789600,
"sys": {
"type": 1,
"id": 5091,
"message": 0.0103,
"country": "GB",
"sunrise": 1485762037,
"sunset": 1485794875
},
"id": 2643743,
"name": "London",
"cod": 200
}
参考代码：
var testJSON = //在帖子中的JSON
var parsed interface{}
json.Unmarshal(testJSON, &parsed)
parsedMap := parsed.(map[string]interface{})
mainTemp := parsedMap["weather"]
fmt.Println(mainTemp)
英文:
The following is the JSON file I'm trying to parse (OpenWeatherMap API if anyone is curious). The builtin encoding/json does a pretty good job of it. When I use json.Unmarshal(testJson, &parsed), most of the JSON file is parsed correctly. However, with the way that it is formatted, the "weather" is giving me a headache.
I parsed the file generated by encoding/json with parsedMap := parsed.(map[string]interface{}), which works when I try to refer to key,value pair with the key "main".
With fmt.Println(), the value is map[temp:280.32 pressure:1012 humidity:81 temp_min:279.15 temp_max:281.15], which I can work with.
With the key "weather" however, I get this [map[icon:09d id:300 main:Drizzle description:light intensity drizzle]]. The additional square brackets seem to be causing issues.
{
"coord": {
"lon": -0.13,
"lat": 51.51
},
"weather": [
{
"id": 300,
"main": "Drizzle",
"description": "light intensity drizzle",
"icon": "09d"
}
],
"base": "stations",
"main": {
"temp": 280.32,
"pressure": 1012,
"humidity": 81,
"temp_min": 279.15,
"temp_max": 281.15
},
"visibility": 10000,
"wind": {
"speed": 4.1,
"deg": 80
},
"clouds": {
"all": 90
},
"dt": 1485789600,
"sys": {
"type": 1,
"id": 5091,
"message": 0.0103,
"country": "GB",
"sunrise": 1485762037,
"sunset": 1485794875
},
"id": 2643743,
"name": "London",
"cod": 200
}
Code for reference:
var testJSON = //JSON EARLIER IN THE POST
var parsed interface{}
json.Unmarshal(testJSON, &parsed)
parsedMap := parsed.(map[string]interface{})
mainTemp := parsedMap["weather"]
fmt.Println(mainTemp)
答案1
得分: 1
你应该首先对weather进行类型断言，将其断言为一个interface{}数组。
然后对第一个元素进行相同的类型断言，将其断言为一个map[string]interface{}。
示例代码如下：
temps := parsedMap["weather"].([]interface{})
mainTemp := temps[0].(map[string]interface{})
你可以在这里查看完整的示例：https://play.golang.org/p/JIfCGrsYl9
英文:
You should first perform a Type assertions on weather as an array of interface{}.
Then do the same on the first element as a map[string]interface{}
temps := parsedMap["weather"].([]interface{})
mainTemp := temps[0].(map[string]interface{})
You can see a full example here https://play.golang.org/p/JIfCGrsYl9
答案2
得分: 0
问题是你需要将其转换为[]interface{}类型。
然而，你应该使用JSON to Go来轻松生成你期望的JSON的结构体类型。你可以删除你不感兴趣的任何字段。
这样可以节省很多类型转换（和错误检查）！
英文:
The issue is that you need to cast as a []interface{}.
However, you should have a look at using JSON to Go to easily generate a struct type for the JSON you expect. You can strip out any fields you're not interested in.
Saves a lot of type-casting (and error checking)!
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