Golang使用Gorm查询数据库并在http响应中返回json

Question

I'm new to Go and am using Gorm to query my postgres database but am having trouble returning my data in a dictionary format, where the pokemon's type serves as a key to an array of all the pokemon of that type

json: cannot unmarshal object into Go value of type []models.Pokemon

here's my code:

type Pokemon struct {
    Name   string   `db:"name"`
    Type   string   `db:"type"`
}

pokemonTypes := [6]string{
    "fire",
    "electric",
    "water",
    "grass",
}

var retData struct {
   Poke []Pokemon
}

m := make(map[string][]Pokemon)

for _, t := range pokemonTypes {
    pokemon := DB.Where(&Pokemon{Type: t}).Find(&retData.Poke)
    p, _ := json.Marshal(pokemon)
    err = json.Unmarshal(p, &retData.Poke)  // getting error here
    if err != nil {
        fmt.Println(err)
    }
    m[category] = retData.Poke
}

data, _ := json.Marshal(m) 
w.Write(data)  // http repsonse

I have this in my database

name       | type
----------------------
pikachu    | electric
charmander | fire
blaziken   | fire
venusaur   | grass
treeko     | grass
squirtle   | water

I want to return data in this json format

{
  “electric”: [
    {"name": "pikachu", "type": "electric"},
  ],
  "fire": [
    {"name": "charmander", "type": "fire"},
    {"name": "blaziken", "type": "fire"}
  ],
  "grass": [
    {"name": "venusaur", "type": "grass"},
    {"name": "treeko", "type": "grass"},
  ],
  "water": [
    {"name": "squirtle", "type": "water"},
  ]
}

Answer 1

DB.Where(&Pokemon{Type: t}).Find(&retData.Poke) esentially returns back the *db pointer which you can use to chain further methods. You're already deserializing postgre rows into your struct slice when you do .Find(&retData.Poke). Thus, pokemon isn't actually what you think it is.

The only thing left now is to chain .Find() with a .Error() so that you can return and check any error in your query. Just like this :

for _, t := range pokemonTypes {
    err := DB.Where(&Pokemon{Type: t}).Find(&retData.Poke).Error()
    if err != nil {
        fmt.Println(err)
        return
    }
    p, _ := json.Marshal(retData.Poke)
    err = json.Unmarshal(p, &retData.Poke) 
    if err != nil {
        fmt.Println(err)
        return
    }
    m[category] = retData.Poke
}

Hope it helps!