如何解组不同数据类型的JSON数组？

Question

Part of the JSON I'm trying to unmarshal has an array that can contain either strings or ints. How would I go about parsing this?

{
    "id": "abc",
    "values": [1,2,3]
},
{
    "id": "def",
    "values": ["elephant", "tomato", "arrow"]
},
{
    //etc...
}

I tried the following:

type Thing struct {
    ID      string   `json:"id"`
    Values  []string `json:"values,string,omitempty"`
}

Get the following error:

panic: json: cannot unmarshal array into Go struct field Thing.values of type string

Answer 1

You can set the type of the field Values to []interface{}, but you might have to use some type assertions.

Here is a link to a playground where I use the data you provided: https://play.golang.org/p/ahePgggr8o1

I will paste the code here anyways:

package main

import (
    "fmt"
    "encoding/json"
)

type Thing struct {
    ID      string   `json:"id"`
    Values  []interface{} `json:"values,omitempty"`
}

func print(values []interface{}) {
    for _, v := range values{
        switch value := v.(type){
        case string:
            fmt.Println("String", value)
        case int:
            fmt.Println("Integer", value)
        case float64:
            fmt.Println("Floats", value)
        default:
            fmt.Printf("I don't know about type %T!
", v)
        }
    }
}

func main() {
    var t1, t2 Thing
    data := []byte("{ \"id\": \"abc\", \"values\": [1,2,3]}")
    data2 := []byte("{ \"id\": \"def\", \"values\": [\"elephant\", \"tomato\", \"arrow\"]}")
    _ = json.Unmarshal(data, &t1)
    _ = json.Unmarshal(data2, &t2)
    print(t1.Values)
    print(t2.Values)
}