Let the node tree to json in golang? - json

Question

I have a tree like the following, and want to save as json format?
package main
import ( "fmt")
type Node struct {
Id string
Nodes []*Node
}
func main() {
node1 := Node{Id: "1"}
node2 := Node{Id:"2"}
node3 := Node{Id: "3"}
node4 := Node{Id: "4"}
node1.Nodes = append(node1.Nodes, &node2)
node2.Nodes = append(node2.Nodes, &node3)
node3.Nodes = append(node3.Nodes, &node4)
fmt.Printf("node1: %p %v \n", &node1, node1)
}
the output json i want is like this ,and how to do it?:
{
Id:"1",
Nodes:[
Id:"2",
Nodes:[
Id:"3",
Nodes:[Id:"4",Nodes:[]]
],
]
}

Answer 1

The following code should do what you want:
package main
import (
"encoding/json"
"fmt"
"log"
)
type Node struct {
Id string
Nodes []*Node
}
func main() {
node1 := Node{Id: "1"}
node2 := Node{Id: "2"}
node3 := Node{Id: "3"}
node4 := Node{Id: "4"}
node1.Nodes = append(node1.Nodes, &node2)
node2.Nodes = append(node2.Nodes, &node3)
node3.Nodes = append(node3.Nodes, &node4)
fmt.Printf("node1: %p %v \n", &node1, node1)
bytes, err := json.Marshal(node1)
if err != nil {
log.Fatal(err)
}
fmt.Println(string(bytes))
}
This code will output json like so:
{
"Id": "1",
"Nodes": [
{
"Id": "2",
"Nodes": [
{
"Id": "3",
"Nodes": [
{
"Id": "4",
"Nodes": null
}
]
}
]
}
]
}
*Notice, that if a Nodes field has no slice of Node objects the field will be marshaled as a null value in the resulting json. If you want the Nodes slice to render as empty, you will have to make sure they are initialized to an empty slice.
Play with this code on the playground here!