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

// 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.

Here’s an example code demonstrating multiple interfaces in Go:

Go

package main

import "fmt"

type Reader interface {
    Read() string
}

type Writer interface {
    Write(string)
}

type ReadWriter interface {
    Reader
    Writer
}

type Document struct {
    content string
}

func (d Document) Read() string {
    return d.content
}

func (d *Document) Write(content string) {
    d.content = content
}

func main() {
    doc := &Document{content: "Initial content"}

    // using the Reader interface to read the document content
    var r Reader = doc
    fmt.Println("Content before writing:", r.Read())

    // using the Writer interface to write new content to the document
    var w Writer = doc
    w.Write("New content")

    // using the ReadWriter interface to read the updated document content
    var rw ReadWriter = doc
    fmt.Println("Content after writing:", rw.Read())
}

Output:

Content before writing: Initial content
Content after writing: New content
 

In this example, we define three interfaces: Reader, Writer, and ReadWriter. The ReadWriter interface embeds both the Reader and Writer interfaces.

We then define a Document struct that has a content string field. We implement the Read method on the Document type to return the value of the content field, and the Write method to update the content field with a new value.

In the main function, we create a new Document instance and assign it to the doc variable. We then use the Reader interface to read the initial content of the document, followed by the Writer interface to write new content to the document. Finally, we use the ReadWriter interface to read the updated content of the document.