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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