unsupported destination, should be slice or struct

[littletwolee]

What version of Go are you using (go version)?

golang 1.8.3

Which database and its version are you using?

mysql 5.6

What did you do?

Please provide a complete runnable program to reproduce your issue.

package main

import (
	"fmt"

	_ "github.com/go-sql-driver/mysql"
	"github.com/jinzhu/gorm"
)

var db *gorm.DB

func find(v *map[string]interface{}) {

}

func main() {
	var err error
	db, err = gorm.Open("mysql", "***")
	if err != nil {
		panic(err)
	}
	var user map[string]interface{}
	db.Debug().Table("test").Find(&user)
	fmt.Println(user)
}

Like this demo.I want search some rows from mysql, and I don't want use struct. Beacuse, when I want get a join result, I need to create a new big struct or to payload struct. I think map is good in this.

Any guys can help me ?Thx

[ktsakas]

You have not initialized the user struct.
Try changing it to var user = make(map[string]interface{}).
Although I think only structs and slices are allowed.
I don't think it works with maps.

[littletwolee]

thx @ktsakas . I was tryed your suggest.But it not work. I think you are right, it is only struct or slices.

[martinskou]

Maybe this can be of help:

package main

import (
	"fmt"
	"reflect"

	"github.com/jinzhu/gorm"
	_ "github.com/mattn/go-sqlite3"
)

type Project struct {
	gorm.Model
	Name string `gorm:"type:varchar(200)"`
}

func main() {
	db, _ := gorm.Open("sqlite3", "db.sqlite3?cache=shared&mode=rwc")
	db.AutoMigrate(&Project{})

	db.Create(&Project{Name: "A"}) // Demo record inserted

	// Now I would like to use reflection to be able to make a generic function
	t := reflect.TypeOf(Project{})
	fmt.Println(t)

	single := reflect.New(t).Interface()
	db.Debug().Table("projects").First(single)
	fmt.Printf("Single result > %+v\n", single) // Works with a single instance

	multiple := reflect.MakeSlice(reflect.SliceOf(t), 0, 10)
	db.Debug().Table("projects").Find(&multiple)       // Log show table and records are found
	fmt.Printf("1. Multiple result > %+v\n", multiple) // But, multiple is empty

	// Instead:

	// Create a pointer to a slice value and set it to the slice
	// multiple := reflect.MakeSlice(reflect.SliceOf(t), 0, 10)
	multiplepointer := reflect.New(multiple.Type())
	multiplepointer.Elem().Set(multiple)

	db.Debug().Table("projects").Find(multiplepointer.Interface())
	fmt.Printf("2. Multiple result > %+v\n", multiplepointer) // multiplepointer contains rows
}