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.NumField() Function in Golang is used to get the number of fields in the struct v. To access this function, one needs to imports the reflect package in the program.
Syntax:
func (v Value) NumField() intParameters: This function does not accept any parameter.
Return Value: This function returns the number of fields in the struct v.
Below examples illustrate the use of the above method in Golang:
Example 1:
// Golang program to illustrate // reflect.NumField() Function package main import ( "fmt"
"reflect"
) // Main function func main() { // use of StructOf method
tt:= reflect.StructOf([]reflect.StructField{
{
Name: "Height" ,
Type: reflect.TypeOf(0.0),
Tag: `json: "height" `,
},
{
Name: "Name" ,
Type: reflect.TypeOf( "abc" ),
Tag: `json: "name" `,
},
})
fmt.Println(tt.NumField())
} |
Output:
2
Example 2:
// Golang program to illustrate // reflect.NumField() Function package main import ( "fmt"
"reflect"
) type temp struct {
ord int
cId int
} // function to use the // Field() method func useKind(val interface{}) { // Kind() function is used
// to find the kind
if reflect.ValueOf(val ).Kind() == reflect.Struct {
v := reflect.ValueOf(val )
fmt.Println( "Number of fields" , v.NumField())
for i := 0; i < v.NumField(); i++ {
fmt.Printf( "Field: %d \t type: %T \t value: %v\n" ,
i, v.Field(i), v.Field(i))
}
}
} // Main function func main() { val := temp {
ord: 1,
cId: 513,
}
useKind(val)
} |
Output:
Number of fields 2 Field: 0 type: reflect.Value value: 1 Field: 1 type: reflect.Value value: 513