英文:
how to build a nested, dynamic JSON in Go
问题
我正在使用Go编写一个简单的API，它从数据库中读取数据并输出GeoJSON。
我已经成功实现了对简单点的处理。但是我的一些数据是线（linestring）。我想要有一个通用的GeoJSON结构定义。然而，根据GeoJSON的规定，“Features”元素有一个“Coordinates”子元素，它可以包含一个[2]float32类型的点坐标，或者是线和多边形的点数组。
在Go中有没有一种方法可以定义这样的结构？我来自PHP，那里有弱类型数组，这样的操作非常简单。
如果我不能使用结构体，除了拼接字符串之外，在Go中还有什么其他适当的方法吗？
注意：类似的问题都是关于从动态JSON进行解组。我需要根据数据库内容构建一个GeoJSON。
英文:
I'm writing a simple API in Go that reads from a database and outputs GeoJSON.
I have this working for simple points. But some of my data is lines (linestring). I would like to have a generic GeoJSON struct definition. However, as specified in GeoJSON, the "Features" element has a "Coordinates" sub-element, which contains either a [2]float32 point coordinates, OR an array of points for lines and polygons.
Is there a way to define a struct in Go in such a way? I come from PHP and with the weakly typed arrays there it would be trivial.
If I can't do it with a struct - what else except puzzling together a string is the proper approach in Go?
Note: Similar questions are all about unmarshaling a dynamic JSON. I need to build one from the database contents.
答案1
得分: 2
你可以创建一个map[string]any，为Coordinates设置其值，然后进行编组（marshal）操作。例如，可以按照以下方式进行操作：
package main
import (
"encoding/json"
"fmt"
)
type Point struct {
X, Y int
}
func main() {
m := map[string]interface{}{}
var singleCoordinate bool
if singleCoordinate {
m["Coordinates"] = []float32{1, 2}
} else {
m["Coordinates"] = []Point{{X: 1, Y: 2}, {X: 2, Y: 2}}
}
data, err := json.Marshal(m)
fmt.Println(string(data), err)
}
Playground: https://go.dev/play/p/8mJHJ-e-kyX
英文:
You can create a map[string]any, set its value for Coordinates and then marshal that.
Like this for example:
package main
import (
"encoding/json"
"fmt"
)
type Point struct {
X, Y int
}
func main() {
m := map[string]any{}
var singleCoordinate bool
if singleCoordinate {
m["Coordinates"] = []float32{1, 2}
} else {
m["Coordinates"] = []Point{{X: 1, Y: 2}, {X: 2, Y: 2}}
}
data, err := json.Marshal(m)
fmt.Println(string(data), err)
}
Playground: https://go.dev/play/p/8mJHJ-e-kyX
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