reflect.Pointer() Function in Golang with Examples

Go language provides inbuilt support implementation of run-time reflection and allowing a program to manipulate objects with arbitrary types with the help of reflect package. The reflect.Pointer() Function in Golang is used to get the v’s value as a uintptr. To access this function, one needs to imports the reflect package in the program.

Syntax:

func (v Value) Pointer() uintptr

Parameters: This function does not accept any parameter.

Return Value: This function returns the v’s value as a uintptr.

Below examples illustrate the use of the above method in Golang:

Example 1:

// Golang program to illustrate
// reflect.Pointer() Function

package main

import (
    "reflect"
    "unsafe"
    "fmt"
)

func main() {
    var s = struct{ foo int }{100}
    var i int

    rs := reflect.ValueOf(&s).Elem()
    rf := rs.Field(0)
    ri := reflect.ValueOf(&i).Elem()

    // use of Pointer() method
    rf = reflect.NewAt(rf.Type(), unsafe.Pointer(rf.UnsafeAddr())).Elem()
    ri.Set(rf)
    rf.Set(ri)

    fmt.Println(rf)
}

Output:

100

Example 2:

// Golang program to illustrate
// reflect.Pointer() Function

package main

import (
    "fmt"
    "play.ground/foo"
    "reflect"
    "unsafe"
)

func GetUnexportedField(field reflect.Value) interface{} {
    return reflect.NewAt(field.Type(), unsafe.Pointer(field.UnsafeAddr())).Elem().Interface()
}

func SetUnexportedField(field reflect.Value, value interface{}) {
    reflect.NewAt(field.Type(), unsafe.Pointer(field.UnsafeAddr())).
        Elem().
        Set(reflect.ValueOf(value))
}

func main() {
    f := &foo.Foo{
        Exported: "Old Value ",
    }

    fmt.Println(f.Exported)

    field := reflect.ValueOf(f).Elem().FieldByName("unexported")
    SetUnexportedField(field, "New Value")
    fmt.Println(GetUnexportedField(field))
}

-- go.mod --
module play.ground

-- foo/foo.go --
package foo

type Foo struct {
    Exported   string
    unexported string
}

Output:

Old Value 
New Value