Job Ready Go

Lesson 15Adding Interfaces

In the previous lessons, we've covered a number of different types that Go supports. Go supports another type as well: interfaces. In its basic form, an interface in Go is a named collection of method signatures without any implementation.

LEARNING OBJECTIVES

By the end of this lesson, you will be able to:

• Create an interface.
• Use an interface with multiple types.
• Work with static and dynamic interface types.
• Apply multiple interfaces.
• Embed an interface.

CREATING AN INTERFACE

If you have worked with object-oriented languages before, then you might already be familiar with the concept of an interface. In Go we can define an interface type using the type and interface keywords:

type Name interface {
    // methods
}

After creating an interface, we can create variables based on that interface. The values stored in those variables implement the methods of the interface.

In other programming languages, such as Java, we normally use the implements keyword to implement an interface. In Go programming, we use the simple convention that the value of an interface type can only hold values of a type that implements the methods of the interface. To understand the concept of interfaces, consider the code in Listing 15.1.

LISTING 15.1Creating an interface

package main
 
import "fmt"
 
type AccountOperations interface{
   // methods
   withdraw(value float64) bool
   deposit(value float64) bool
   displayInfo()
}
 
type account struct {
   number string
 balance ...