Advanced Techniques in Go Programming/

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Changing Structure Values Using Reflection

Changing Structure Values Using Reflection

Let’s learn how to change values using reflection in the Go structure.

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Learning about the internal structure of a Go structure is handy, but what is more practical is being able to change values in the Go structure, which is the subject of this lesson.

Coding example

Let’s look at the setValues.go code:

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package main
import (
	"fmt"
	"reflect"
)
type T struct {
	F1 int
	F2 string
	F3 float64
}

In the code above, we define a struct type named T with three fields: F1 of type int, F2 of type string, and F3 of type float64.

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func main() {
	A := T{1, "F2", 3.0}
	fmt.Println("A:", A)
	r := reflect.ValueOf(&A).Elem()
	fmt.Println("String value:", r.String())
	typeOfA := r.Type()
	for i := 0; i < r.NumField(); i++ {
		f := r.Field(i)
		tOfA := typeOfA.Field(i).Name
		fmt.Printf("%d: %s %s = %v\n", i, tOfA, f.Type(), f.Interface())
		k := reflect.TypeOf(r.Field(i).Interface()).Kind()
		if k == reflect.Int {
			r.Field(i).SetInt(-100)
		} else if k == reflect.String {
			r.Field(i).SetString("Changed!")
		}
	}
	fmt.Println("A:", A)
}

In the code above, A is the variable that is examined in this program. ...