Promoted Methods in Golang Structure

In Go structure, the working of promoted methods is just like Promoted Fields. We use this concept in the nested structure where a structure is a field in another structure, simply by just adding the name of the structure into another structure and it behaves like the Anonymous Field to the nested structure. And the methods of that structure (other than nested structure) are the part of the nested structure, such type of methods are known as Promoted Methods. Or in other words, prompted methods are those methods which are implemented by the child structure, and is accessible by the parent structure.

Important Points:

• If the child and the parent structure contain a method that has the same name but different type of receiver, then both the methods are available in the parent structure as shown in Example 2. Here both child and parent structure contain methods of the same names.
• If child structure contains two methods with the same name and same receiver, then these methods are not promoted in the parent structure and if you try to do, then the compiler will give an error.

Example 1:

// Golang program to illustrate the
// concept of the promoted methods
package main

import "fmt"

// Structure
type details struct {

    // Fields of the
    // details structure
    name    string
    age     int
    gender  string
    psalary int
}

// Nested structure
type employee struct {
    post string
    eid  int
    details
}

// Method
func (d details) promotmethod(tsalary int) int {
    return d.psalary * tsalary
}

func main() {

    // Initializing the fields of
    // the employee structure
    values := employee{
        post: "HR",
        eid:  4567,
        details: details{

            name:    "Sumit",
            age:     28,
            gender:  "Male",
            psalary: 890,
        },
    }

    // Promoted fields of the
    // employee structure
    fmt.Println("Name: ", values.name)
    fmt.Println("Age: ", values.age)
    fmt.Println("Gender: ", values.gender)
    fmt.Println("Per day salary: ", values.psalary)

    // Promoted method of the
    // employee structure
    fmt.Println("Total Salary: ", values.promotmethod(30))

    // Normal fields of
    // the employee structure
    fmt.Println("Post: ", values.post)
    fmt.Println("Employee id: ", values.eid)
}

Output:

Name:  Sumit
Age:  28
Gender:  Male
Per day salary:  890
Total Salary:  26700
Post:  HR
Employee id:  4567

Example 2:

// Golang program to illustrate the
// concept of the promoted methods
package main

import "fmt"

// Structure
type details struct {

    // Fields of the
    // details structure
    name    string
    age     int
    gender  string
    psalary int
}

// Method 1
func (e employee) promotmethod(tarticle int) int {
    return e.particle * tarticle
}

// Nested structure
type employee struct {
    post     string
    particle int
    eid      int
    details
}

// Method 2
func (d details) promotmethod(tsalary int) int {
    return d.psalary * tsalary
}

// Main method
func main() {

    // Initializing the fields of
    // the employee structure
    values := employee{
        post:     "HR",
        eid:      4567,
        particle: 5,
        details: details{

            name:    "Sumit",
            age:     28,
            gender:  "Male",
            psalary: 890,
        },
    }

    // Promoted fields of
    // the employee structure
    fmt.Println("Name: ", values.name)
    fmt.Println("Age: ", values.age)
    fmt.Println("Gender: ", values.gender)
    fmt.Println("Per day salary: ", values.psalary)

    // Promoted method of
    // the employee structure
    fmt.Println("Total Salary: ", values.promotmethod(30))

    // Normal fields of
    // the employee structure
    fmt.Println("Post: ", values.post)
    fmt.Println("Employee id: ", values.eid)
    fmt.Println("Total Articles: ", values.promotmethod(30))
}

Output:

Name:  Sumit
Age:  28
Gender:  Male
Per day salary:  890
Total Salary:  150
Post:  HR
Employee id:  4567
Total Articles:  150