CODEWITHSUNDEEP
jsongostructunmarshalling
aniztar
aniztar

Reputation: 2913

Empty fields while doing json unmarshal

I have written this piece of code. I can't figure out why it is giving empty fields when i run it. I have tried Uppercase variables. Still doesn't work. 

package main

import (
        "encoding/json"
        "fmt"
)

type FirstName struct {
        Name1 string
}
type SecondName struct {
        Name2 string
}
type Person struct {
        Details     FirstName
        MoreDetails SecondName
}

func main() {
        var someGuy Person
        var data = []byte(`{"details": {"firstName": "alan"}, "moreDetails": {"surName": "Turing"}}`)
        json.Unmarshal(data, &someGuy)
        fmt.Println(someGuy)
}

Upvotes: 4

Views: 2679

Answers (1)

icza
icza

Reputation: 417602

Your JSON to Go mapping is incorrect. To have automatic matching between struct fields and the JSON properties during the unmarshaling process, the field names (and not the name of their types) must match the properties in JSON (in a case in-sensitive manner):

type FirstName struct {
    FirstName string
}
type SecondName struct {
    SurName string
}
type Person struct {
    Details     FirstName
    MoreDetails SecondName
}

With this, the output is (try it on the Go Playground):

{{alan} {Turing}}

If you want to keep those names in Go, another option is to provide a mapping between Go struct fields and JSON property names. For this you may use struct tags:

type FirstName struct {
    Name1 string `json:"firstName"`
}
type SecondName struct {
    Name2 string `json:"surName"`
}

Output will be the same. Try this one on the Go Playground.

For an introduction and more details about struct tags, see What are the use(s) for tags in Go?

Upvotes: 7

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