How to make nested JSON response in Go? - json

Question

I am new in Go and need some help.
In my PostgreSQL database I have 4 table. They called: surveys, questions, options and surveys_questions_options.
They looks like this:
surveys table:
| survey_id (uuid4) | survey_name (varchar) |
|--------------------------------------|-----------------------|
| 0cf1cf18-d5fd-474e-a8be-754fbdc89720 | April |
| b9fg55d9-n5fy-s7fe-s5bh-856fbdc89720 | May |
questions table:
| question_id (int) | question_text (text) |
|-------------------|------------------------------|
| 1 | What is your favorite color? |
options table:
| option_id (int) | option_text (text) |
|-------------------|--------------------|
| 1 | red |
| 2 | blue |
| 3 | grey |
| 4 | green |
| 5 | brown |
surveys_questions_options table combines data from all three previous tables:
| survey_id | question_id | option_id |
|--------------------------------------|-------------|-----------|
| 0cf1cf18-d5fd-474e-a8be-754fbdc89720 | 1 | 1 |
| 0cf1cf18-d5fd-474e-a8be-754fbdc89720 | 1 | 2 |
| 0cf1cf18-d5fd-474e-a8be-754fbdc89720 | 1 | 3 |
| b9fg55d9-n5fy-s7fe-s5bh-856fbdc89720 | 1 | 3 |
| b9fg55d9-n5fy-s7fe-s5bh-856fbdc89720 | 1 | 4 |
| b9fg55d9-n5fy-s7fe-s5bh-856fbdc89720 | 1 | 5 |
How can I make nested JSON response in Go? I use GORM library. I want a JSON response like this:
[
{
"survey_id": "0cf1cf18-d5fd-474e-a8be-754fbdc89720",
"survey_name": "April",
"questions": [
{
"question_id": 1,
"question_text": "What is your favorite color?",
"options": [
{
"option_id": 1,
"option_text": "red"
},
{
"option_id": 2,
"option_text": "blue"
},
{
"option_id": 3,
"option_text": "grey"
},
]
}
]
},
{
"survey_id": "b9fg55d9-n5fy-s7fe-s5bh-856fbdc89720",
"survey_name": "May",
"questions": [
{
"question_id": 1,
"question_text": "What is your favorite color?",
"options": [
{
"option_id": 3,
"option_text": "grey"
},
{
"option_id": 4,
"option_text": "green"
},
{
"option_id": 5,
"option_text": "brown"
},
]
}
]
}
]
My models looks like this:
type Survey struct {
SurveyID string `gorm:"primary_key" json:"survey_id"`
SurveyName string `gorm:"not null" json:"survey_name"`
Questions []Question
}
type Question struct {
QuestionID int `gorm:"primary_key" json:"question_id"`
QuestionText string `gorm:"not null;unique" json:"question_text"`
Options []Option
}
type Option struct {
OptionID int `gorm:"primary_key" json:"option_id"`
OptionText string `gorm:"not null;unique" json:"option_text"`
}

Answer 1

I'm not sure abour GORM part, but with JSON you need to add struct tags on the nested objects as well:
type Survey struct {
...
Questions []Question `json:"questions"`
}
type Question struct {
...
Options []Option `json:"options"`
}

Answer 2

We're missing some scope from your code, and so it's quite hard to point you in the right direction. Are you asking about querying GORM so you get []Survey, or are you asking about marshalling []Survey? Anyway, you should add the tag to Questions too, as slomek replied.

Answer 3

However, try this:
To fetch nested data in m2m relation
type Survey struct {
gorm.Model
SurveyID string `gorm:"primary_key" json:"survey_id"`
SurveyName string `gorm:"not null" json:"survey_name"`
Questions []*Question `gorm:"many2many:survey_questions;"`
}
surveys := []*model.Survey{}
db := dbSession.Where(&model.Survey{SurveyID: id}).Preload("Questions").Find(&surveys)