How to pass multiple data objects to HTML templates in Golang - parsing

Question

I am returing all rows of a table as json to the variable pdata and unmarshaling it into an interface object.
I have an instance of the user struct which I would like to pass along with the unmarshalled json data to the render function and access it using field arguments {{.fieldname}} in the html template.
if uuid != "" {
pdata, err := getProduct()
if err != nil {
fmt.Println(err)
}
type Prdata struct {
Puid string `json:"puid"`
Pname string `json:"pname"`
Quantity string `json:"quantity"`
Price string `json:"price"`
Image string `json:"image"`
}
// Obj:= make(map[Prdata]string)
var Pr Prdata
err = json.Unmarshal(pdata , &Pr)
if err != nil {
fmt.Println(err)
}
fmt.Println(string(pdata))
fmt.Println(Pr)
fmt.Println(u)
render(w, "internal", Pr)
}
fmt.Println(string(pdata)) gives this output
[{"image":"1Appleiphone7.jpeg","pname":"iphone7","price":"70000","puid":"d6742e4e-2ad6-43c5-97f4-e8a7b00684e2","quantity":"100"}]
I have only been successful to unmarshal the data into an interface{} object. Trying to make maps with keys of the type interface{} and values of type string but it throws the error:
"json: cannot unmarshal array into Go value of type map[interface {}]string"
The render function takes an argument of the type interface{}
func render(w http.ResponseWriter, name string, data interface{})
fmt.Println(Pr) gives this output:
[map[quantity:100 image:1Appleiphone7.jpeg pname:iphone7 price:70000 puid:d6742e4e-2ad6-43c5-97f4-e8a7b00684e2]]
u is an instance of struct User
var u = &User{}
type User struct {
Uuid string
Username string
Password string
Fname string
Email string
}
I can see the output on the html page using the pipeline {{.}}. However I am not able to access any data using the fieldname.
There must be a way of doing this. But I am not sure how?
When I pass of a json of the type below, I am able to pass it to the struct type and reference it by the key values using pipelines in my template.
str := `{
"image": "1Appleiphone7.jpeg",
"pname": "iphone7",
"price": "70000",
"puid": "d6742e4e-2ad6-43c5-97f4-e8a7b00684e2",
"quantity": "100"
}`
unmarshal function
err = json.Unmarshal([]byte(str), &Pr)
The difference in the json data of the DB record pdata and the one above str is in the use of backticks "`". It seems that though the json data shows key value pairs, it is actually a json array and not a json object. Is there a way to get around this?

Answer 1

You don't need a map[interface{}]string to unmarshal the json obj. Your json is equivalent to slice of maps:
[
{
"image":"1Appleiphone7.jpeg",
"pname":"iphone7",
"price":"70000",
"puid":"d6742e4e-2ad6-43c5-97f4-e8a7b00684e2",
"quantity":"100"
}
]
The object to unmarshal should be a slice of maps with string keys and values:
var Pr []map[string]string
Playground
BTW, I believe misunderstanding is hidden there:
The render function takes an argument of the type interface{}
I means not that you must pass a variable of interface{} type there but it means you CAN pass a variable of any type to render function.

Answer 2

I am posting a working example of unmarshalling json as bytes into a struct type which then can be referenced using the {{.}} in the template.
package main
import (
"encoding/json"
"fmt"
)
type Usrdata struct {
Uuid string
Fname string
}
type Prdata struct {
Puid string `json:"puid"`
Pname string `json:"pname"`
Quantity string `json:"quantity"`
Price string `json:"price"`
Image string `json:"image"`
}
type Data struct {
U Usrdata
P []Prdata
}
func main() {
Ur := Usrdata{Uuid: "xyz", Fname: "Somename"}
Pr := make([]Prdata, 0)
var Dt Data
Dt.U = Ur
pdata := `[{"image":"1Appleiphone7.jpeg","pname":"iphone7","price":"70000","puid":"d6742e4e-2ad6-43c5-97f4-e8a7b00684e2","quantity":"100"}]`
err := json.Unmarshal([]byte(pdata), &Pr)
if err != nil {
fmt.Println(err)
}
Dt.P = Pr
fmt.Println(Pr[0].Pname)
fmt.Println(Pr)
fmt.Println(Dt)
}