How do you create a new instance of a struct from its type at run time in Go?

In Go, how do you create the instance of an object from its type at run time? I suppose you would also need to get the actual type of the object first too?

I am trying to do lazy instantiation to save memory.

In order to do that you need reflect.

package main

import (
    "fmt"
    "reflect"
)

func main() {
    // one way is to have a value of the type you want already
    a := 1
    // reflect.New works kind of like the built-in function new
    // We'll get a reflected pointer to a new int value
    intPtr := reflect.New(reflect.TypeOf(a))
    // Just to prove it
    b := intPtr.Elem().Interface().(int)
    // Prints 0
    fmt.Println(b)

    // We can also use reflect.New without having a value of the type
    var nilInt *int
    intType := reflect.TypeOf(nilInt).Elem()
    intPtr2 := reflect.New(intType)
    // Same as above
    c := intPtr2.Elem().Interface().(int)
    // Prints 0 again
    fmt.Println(c)
}

You can do the same thing with a struct type instead of an int. Or anything else, really. Just be sure to know the distinction between new and make when it comes to map and slice types.

Stack Overflow Q#7850140, score: 112