Multiple Interfaces in Golang

In Go language, the interface is a collection of method signatures and it is also a type means you can create a variable of an interface type. In Go language, you are allowed to create multiple interfaces in your program with the help of the given syntax:

type interface_name interface{

// Method signatures

}

Note: In Go language, you are not allowed to create same name methods in two or more interfaces. If you try to do so, then your program will panic. Let us discuss multiple interfaces with the help of an example.

Example:

// Go program to illustrate the
// concept of multiple interfaces
package main

import "fmt"

// Interface 1
type AuthorDetails interface {
    details()
}

// Interface 2
type AuthorArticles interface {
    articles()
}

// Structure
type author struct {
    a_name    string
    branch    string
    college   string
    year      int
    salary    int
    particles int
    tarticles int
}

// Implementing method
// of the interface 1
func (a author) details() {

    fmt.Printf("Author Name: %s", a.a_name)
    fmt.Printf("\nBranch: %s and passing year: %d", a.branch, a.year)
    fmt.Printf("\nCollege Name: %s", a.college)
    fmt.Printf("\nSalary: %d", a.salary)
    fmt.Printf("\nPublished articles: %d", a.particles)

}

// Implementing method
// of the interface 2
func (a author) articles() {

    pendingarticles := a.tarticles - a.particles
    fmt.Printf("\nPending articles: %d", pendingarticles)
}

// Main value
func main() {

    // Assigning values
    // to the structure
    values := author{
        a_name:    "Mickey",
        branch:    "Computer science",
        college:   "XYZ",
        year:      2012,
        salary:    50000,
        particles: 209,
        tarticles: 309,
    }

    // Accessing the method
    // of the interface 1
    var i1 AuthorDetails = values
    i1.details()

    // Accessing the method
    // of the interface 2
    var i2 AuthorArticles = values
    i2.articles()

}

Output:

Author Name: Mickey
Branch: Computer science and passing year: 2012
College Name: XYZ
Salary: 50000
Published articles: 209
Pending articles: 100

Explanation: As shown in the above example we have two interfaces with methods, i.e, details() and articles(). Here, details() method provides the basic details of the author and articles() method provides the pending articles of the author.

And a structure named as an author which contains some set of variables whose values are used in the interfaces. In the main method, we assign the values of the variables present, in the author structure, so that they will use in the interfaces and create the interface type variables to access the methods of the AuthorDetails and AuthorArticles interfaces.