json.Marshal(struct) returns “{}”

Question

type TestObject struct {
    kind string `json:\"kind\"`
    id   string `json:\"id, omitempty\"`
    name  string `json:\"name\"`
    email string `json:\"email\"`
         


        

Answer 1

• When the first letter is capitalised, the identifier is public to any piece of code that you want to use.
• When the first letter is lowercase, the identifier is private and could only be accessed within the package it was declared.

Examples

 var aName // private

 var BigBro // public (exported)

 var 123abc // illegal

 func (p *Person) SetEmail(email string) {  // public because SetEmail() function starts with upper case
    p.email = email
 }

 func (p Person) email() string { // private because email() function starts with lower case
    return p.email
 }

Answer 2

In golang

in struct first letter must uppercase ex. phonenumber -> PhoneNumber

======= Add detail

First, I'm try coding like this

type Questions struct {
    id           string
    questionDesc string
    questionID   string
    ans          string
    choices      struct {
        choice1 string
        choice2 string
        choice3 string
        choice4 string
    }
}

golang compile is not error and not show warning. But response is empty because something

After that, I search google found this article

Struct Types and Struct Type Literals Article then... I try edit code.

//Questions map field name like database
type Questions struct {
    ID           string
    QuestionDesc string
    QuestionID   string
    Ans          string
    Choices      struct {
        Choice1 string
        Choice2 string
        Choice3 string
        Choice4 string
    }
}

Is work.

Hope for help.

Answer 3

You need to export the fields in TestObject by capitalizing the first letter in the field name. Change kind to Kind and so on.

type TestObject struct {
 Kind string `json:"kind"`
 Id   string `json:"id,omitempty"`
 Name  string `json:"name"`
 Email string `json:"email"`
}

The encoding/json package and similar packages ignore unexported fields.

The `json:"..."` strings that follow the field declarations are struct tags. The tags in this struct set the names of the struct's fields when marshaling to and from JSON.

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