commandbus

Installation

Make sure that Go is installed on your computer. Type the following command in your terminal:

go get github.com/dadamssg/commandbus

After it the package is ready to use.

Import package in your project

Add following line in your *.go file:

import "github.com/dadamssg/commandbus"

Example

package main

import (
    "fmt"
    "github.com/dadamssg/commandbus"
)

type RegisterUserCommand struct {
    Username string
}

func main() {
    bus := commandbus.New()

    bus.RegisterHandler(&RegisterUserCommand{}, func(cmd interface{}) {
        command, _ := cmd.(*RegisterUserCommand)
        fmt.Println("Registered: ", command.Username)
    })

    // add a middleware with a priority of 0
    bus.AddMiddleware(0, func(cmd interface{}, next commandbus.HandlerFunc) {
        fmt.Println("Enter mock caching middleware")
        next(cmd)
        fmt.Println("Exit mock caching middleware")
    })

    // add a middleware with a priority of 1
    bus.AddMiddleware(1, func(cmd interface{}, next commandbus.HandlerFunc) {
        fmt.Println("Enter mock logging middleware")
        next(cmd)
        fmt.Println("Exit mock logging middleware")
    })

    bus.Handle(&RegisterUserCommand{
        Username: "David",
    })
}

The above will produce the following output

Enter mock logging middleware
Enter mock caching middleware
Registered:  David
Exit mock caching middleware
Exit mock logging middleware

Why?

I've come to appreciate hexagonal architecture and was missing a package that would allow me to architect an app in such a way.

Structuring an app using a command bus allows you to have several different client interfaces(http, cli, etc.) that are only responsible for creating command structs and sending them into the bus to be handled. A command only has a single handler but you can add as many middleware layers as needed, allowing to easily plug in logging, caching, authentication, etc.