在json.Unmarshal之后接收零初始化的对象

Question

I can't seem to be able to parse a json file in Go. I've tried a bunch of tutorials, but I can't see what I'm doing wrong. The JSON looks like this.

{
    "latitude": 34.4048358,
    "longitude": -119.5313565,
    "dateTime": "Thu Jun 26 2014 08:36:42 GMT-0700 (PDT)"
}

And my main file looks like this.

package main

import (
    "encoding/json"
    "fmt"
)

type Position struct {
    latitude  float64 `json:latitude`
    longitude float64 `json:logitude`
    dateTime  string  `json:dateTime`
}

func jsonToPosition(jsonData []byte) {
    position := &Position{}

    if err := json.Unmarshal(jsonData, position); err != nil {
        fmt.Println(err)
    }

    fmt.Println(position)
}

func main() {
    jsonToPosition([]byte(`{"latitude":34.4048358,"longitude":-119.5313565,"dateTime":"Thu Jun 26 2014 08:36:42 GMT-0700 (PDT)"}`))
}

I don't get an error or anything. I just get &{0 0 } when I do fmt.Println(position).

Answer 1

This is a common mistake: you did not export values in the Position structure, so the json package was not able to use it. Use a capital letter in the variable name to do so:

type Position struct {
    Latitude  float64 `json:latitude`
    Longitude float64 `json:logitude`
    DateTime  string  `json:dateTime`
}