Transform struct to slice struct - go

Question

I'm trying to select a struct by string input and then depending on the return JSON Object or Array, unmarshall the JSON. Is it correct to think of a way to reflect the struct to slice struct? if so how to do that with reflection?
Regards,
Peter
package main
import (
"bytes"
"encoding/json"
"fmt"
"log"
)
type NameStruct struct {
Name string
}
func main() {
jsonData := []byte(`[{"name":"james"},{"name":"steven"}]`)
returnModel := InitializeModel("NameStruct", jsonData)
fmt.Println(returnModel)
jsonData = []byte(`{"name":"james"}`)
returnModel = InitializeModel("NameStruct", jsonData)
fmt.Println(returnModel)
}
func getModelByName(modelType string) interface{} {
modelMap := make(map[string]interface{})
modelMap["NameStruct"] = new(NameStruct)
//don't want to do this
modelMap["arrNameStruct"] = new([]NameStruct)
return modelMap[modelType]
}
func InitializeModel(modelName string, jsonData []byte) interface{} {
switch IsArray(jsonData) {
case true:
// some conversion here, how?
returnModel := getModelByName("NameStruct")
if err := json.Unmarshal(jsonData, &returnModel); err != nil {
log.Println(err)
}
return returnModel
case false:
returnModel := getModelByName("NameStruct")
if err := json.Unmarshal(jsonData, &returnModel); err != nil {
log.Println(err)
}
return returnModel
}
return nil
}
func IsArray(jsonData []byte) bool {
return (bytes.HasPrefix(jsonData, []byte("["))) && (bytes.HasSuffix(jsonData, []byte("]")))
}

Answer 1

Expanding on my comment, you can create a Factory where pre-defined types are registered:
type Factory struct {
m map[string]reflect.Type
}
func (f *Factory) Register(v interface{}) {
vt := reflect.TypeOf(v)
n := vt.Name()
f.m[n] = vt
f.m["[]"+n] = reflect.SliceOf(vt) // implicitly register a slice of type too
}
these types can be looked up by name at runtime and initialized with JSON data:
func (f *Factory) Make(k string, bs []byte) (interface{}, error) {
vt, ok := f.m[k]
if !ok {
return nil, fmt.Errorf("type %q not registered", k)
}
pv := reflect.New(vt).Interface()
err := json.Unmarshal(bs, pv)
if err != nil {
return nil, err
}
return pv, nil
}
To use:
type Place struct {
City string `json:"city"`
}
factory.Register(Place{})
p, err := factory.Make("Place", []byte(`{"city":"NYC"}`))
fmt.Printf("%#v\n", p) // &main.Place{City:"NYC"}
Slices also work:
ps, err := factory.Make("[]Place", []byte(`[{"city":"NYC"},{"city":"Dublin"}]`))
fmt.Printf("%#v\n", p, p) // &[]main.Place{main.Place{City:"NYC"}, main.Place{City:"Dublin"}}
Playground: https://play.golang.org/p/qWEdwk-YUug