How to use Golang to implement interfaces across packages

Golang is an open source programming language that has many advantages, such as efficiency, simplicity, security, etc. It is becoming more and more popular among developers in today's Internet environment. Among them, Golang's interface features are one of its most attractive parts. This article will discuss how to use Golang to implement interfaces across packages.

In Golang, interface is a way of defining behavior. An interface is like a protocol that specifies methods that must be implemented. This approach can improve code reusability and maintainability, while also strengthening code type checking to avoid runtime errors.

In actual development, we often need to define some interfaces and implement them. For example, in a network library, we need to implement a connection pool. The connection pool requires the release and application of connections. We can define an interface and then implement the interface in the connection pool.

However, in the actual code implementation process, we may encounter a problem: the interface definition and implementation code may be in different packages. What should we do at this time? Next, I will demonstrate how to implement interfaces across packages in Golang.

1. Define the interface

First, we need to define an interface. In this example, we define an interface called Connection, and it has two methods: Open() and Close().

package connection

type Connection interface {
    Open() error
    Close()
}

2. Implement the interface

Next, we define a connection structure and then implement the Connection interface. It should be noted that at this time we need to introduce the Connection interface definition into another package. Here we have introduced the connection package.

package mysql

import "github.com/user/connection"

type MySQLConnection struct {
    // connection info
}

func (conn *MySQLConnection) Open() error {
    // connect to mysql
    return nil
}

func (conn *MySQLConnection) Close() {
    // close mysql connection
}

func New() connection.Connection {
    return &MySQLConnection{}
}

In the above code, we define a MySQLConnection structure and implement the Connection interface on it. Finally, we create this structure through a function called New().

3. Introduction of the interface

In the previous step, we introduced the Connection interface definition into the mysql package. Now we need to use this interface in another package app.

package app

import (
    "log"
    "github.com/user/mysql"
    "github.com/user/connection"
)

func main() {
    conn := mysql.New()
    err := conn.Open()
    if err != nil {
        log.Fatalf("error while connecting: %s", err)
    }
    defer conn.Close()

    // use connection

    var _ connection.Connection = conn
}

In the above code, we created a MySQLConnection structure through the mysql.New() function, and then called Open()Method to connect to the database. Next we can use this connection to perform some operations. Finally, we close the connection by defer conn.Close().

It should be noted that we added var _ connection.Connection = conn at the end. This is to ensure that this connection implements the Connection interface.

Through the above examples, I believe you have mastered the method of implementing interfaces across packages in Golang. In actual development, we can use this method to improve code reusability and maintainability and avoid runtime errors.

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