reflect.Set() Function in Golang with Examples

Last Updated : 10 May, 2020

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.Set() Function in Golang is used to assigns x to the value v. To access this function, one needs to imports the reflect package in the program.

Syntax:
func (v Value) Set(x Value)
Parameters: This function accept one parameter of Value type (x).
Return Value: This function does not returns any value.

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

Example 1:

// Golang program to illustrate 
// reflect.Set() Function 
     
package main 
     
import ( 
    "fmt"
    "reflect"
    "unsafe"
) 
     
// Main function 
func main() {
        var s = struct{ foo int }{654}
    var i int
   
    rs := reflect.ValueOf(&s).Elem() 
    rf := rs.Field(0)                
    ri := reflect.ValueOf(&i).Elem() 
   
    rf = reflect.NewAt(rf.Type(), unsafe.Pointer(rf.UnsafeAddr())).Elem()
    ri.Set(rf)
    rf.Set(ri)
    fmt.Println(rf) 
    fmt.Println(ri) 
       
}

Output:

654
654

Example 2:

// Golang program to illustrate
// reflect.Set() Function
     
package main
     
import (
    "fmt"
    "reflect"
)
    
func sum(args []reflect.Value) []reflect.Value {
    a, b := args[0], args[1]
    if a.Kind() != b.Kind() {
        fmt.Println("??? ????.")
        return nil
    }
    
    switch a.Kind() {
    case reflect.Int, reflect.Int8, reflect.Int16,
                     reflect.Int32, reflect.Int64:
        return []reflect.Value{reflect.ValueOf(a.Int() + b.Int())}
  
    case reflect.Uint, reflect.Uint8, reflect.Uint16, 
                      reflect.Uint32, reflect.Uint64:
        return []reflect.Value{reflect.ValueOf(a.Uint() + b.Uint())}
  
    case reflect.Float32, reflect.Float64:
        return []reflect.Value{reflect.ValueOf(a.Float() + b.Float())}
  
    case reflect.String:
        return []reflect.Value{reflect.ValueOf(a.String() + b.String())}
  
    default:
        return []reflect.Value{}
    }
}
    
func makeSum(fptr interface{}) {
    fn := reflect.ValueOf(fptr).Elem()
    
    v := reflect.MakeFunc(fn.Type(), sum)
    
    fn.Set(v)
}
     
// Main function
func main() {
   
    var stringSum func(string, string) string
   
    makeSum(&stringSum)
    
    fmt.Println(stringSum("Value_1 : ", "Geeks_1"))
    
}

Output:

Value_1 : Geeks_1

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reflect.Set() Function in Golang with Examples