GoLang Redis：地图和切片

Question

I'm using GoLang to get a data from redis hash and then map into a struct.

type Person struct {
    ID         string       `json:"id"`
    FirstName  string       `json:"firstName"`
    LastName   string       `json:"lastName"`
    Filters    interface{}  `json:"filters"`
    Type       string       `json:"type"`
}

In Redis, a hash field contains a stringified JSON.

HGET hashname fieldname

Above returns a stringified JSON.

Now "filters" key can be array or map based on the type (That's why I defined Filters type as interface in struct).
I marshall the JSON like below:

var p Person
content, err := redis.HGet("hashName", "id").Result()
_ = json.Unmarshal([]byte(content), &p)

Now I have to loop over filters like below but this is giving error that cannot range over p.Filters (type interface {}) (I understand why this error is coming)

for _, filter := range p.Filters {
  fmt.Println(filter)
}

Is there any way we can handle this situation?

Thanks,
Shashank

Answer 1

You need to convert Filters type interface{} into the expected slice. If you don't really know what type it will be, you can use map[string]interface{}. Therefore change your Filters type to map[string]interface{}.

Per more information If Filters can be an array (or not), then you might consider a type switch:

A simple example:

package main

import (
    "encoding/json"
    "fmt"
)

func main() {
    var i interface{}
    //json.Unmarshal([]byte(`["hi"]`), &i)
    json.Unmarshal([]byte(`{"a":"hi"}`), &i)

    switch i.(type) {
    case []interface{}:
        println("ARRAY")
    case map[string]interface{}:
        println("NOT ARRAY")
    default:
        fmt.Printf("%T
", i)
    }
}