reflect.FieldByIndex() 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.FieldByIndex() Function in Golang is used to get the nested field corresponding to index. To access this function, one needs to imports the reflect package in the program.

Syntax:

func (v Value) FieldByIndex(index []int) Value

Parameters: This function accept only single parameters.

  • index : This parameter is the []int type.

Return Value: This function returns the nested field corresponding to index.

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



Example 1:

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// Golang program to illustrate
// reflect.FieldByIndex() Function 
   
package main
   
import (
    "fmt"
    "reflect"
)
   
// Main function 
func main() {
      
    tt:= reflect.StructOf([]reflect.StructField{
        {
            Name: "Height",
            Type: reflect.TypeOf(0.0),
            Tag:  `json:"height"`,
        },
        {
            Name: "Name",
            Type: reflect.TypeOf("abc"),
            Tag:  `json:"name"`,
        },
    })
      
    // use of FieldByIndex() method
    fmt.Println(tt.FieldByIndex([]int{0}))
  
}    

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Output:

{Height  float64 json:"height" 0 [0] false}

Example 2:

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// Golang program to illustrate
// reflect.FieldByIndex() Function 
   
package main
   
import (
    "fmt"
    "reflect"
)
   
type User struct {
    Id   int
    Name string
    Age  int
}
   
type Manager struct {
         User 
    Title string
}
   
// Main function 
func main() {
      
    m := Manager{User: User{1, "Jack", 12}, Title: "123"}
    t := reflect.TypeOf(m)
         fmt.Printf("%#v\n", t.Field(0)) 
    fmt.Printf("%#v \n", t.Field(1))
      
    // use of FieldByIndex() method
    fmt.Printf("%#v \n", t.FieldByIndex([]int{0, 0}))
    fmt.Printf("%#v \n", t.FieldByIndex([]int{0, 1}))
    fmt.Printf("%#v \n", t.FieldByIndex([]int{0, 2}))
  
}

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Output:

reflect.StructField{Name:”User”, PkgPath:””, Type:(*reflect.rtype)(0x4b1480), Tag:””, Offset:0x0, Index:[]int{0}, Anonymous:true}
reflect.StructField{Name:”Title”, PkgPath:””, Type:(*reflect.rtype)(0x4a1c20), Tag:””, Offset:0x20, Index:[]int{1}, Anonymous:false}
reflect.StructField{Name:”Id”, PkgPath:””, Type:(*reflect.rtype)(0x4a14e0), Tag:””, Offset:0x0, Index:[]int{0}, Anonymous:false}
reflect.StructField{Name:”Name”, PkgPath:””, Type:(*reflect.rtype)(0x4a1c20), Tag:””, Offset:0x8, Index:[]int{1}, Anonymous:false}
reflect.StructField{Name:”Age”, PkgPath:””, Type:(*reflect.rtype)(0x4a14e0), Tag:””, Offset:0x18, Index:[]int{2}, Anonymous:false}




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