di

di

di (dependency-injection) saves you from writing boiler-plate setup code in your main (and elsewhere) function by automating the creation of functions which build the providers you want injected.

Usage

1. Install di
2. Create a provider file.
3. Add a go:generate comment to provider file like so

//go:generate di filename.go

What is a provider file?

First, what is a provider? It's just a function which returns something. That something may be required as a dependency for another provider or not.

A provider file contains all of the definitions for each provider as well as their prerequisites for being built. It's quite literally just a file which contains functions which won't be directly called by your code.

Example More detailed examples can be found within the [examples/|examples/] directory

//go:generate di example.go
package example

import "fmt"

func Path() string {
    return "localhost"
}

func Port() int {
    return 80
}

func Address(host string, port int) string {
    return fmt.Sprintf("%s:%d", host, port)
}

Using the go generate command on example.go would produce the following file

package example

var singleton *ExampleComponent

func GetExampleComponent() *ExampleComponent {
	if singleton == nil {
		singleton = &ExampleComponent{}
	}
	return singleton
}

type ExampleComponent struct {
}

func (c *ExampleComponent) Path() string {
	return Path()
}
func (c *ExampleComponent) Port() int {
	return Port()
}
func (c *ExampleComponent) Address() string {
	return Address(
		c.Path(),
		c.Port(),
	)
}

Which could then be used in your main.go to retrieve a correctly formatted address without having to write the boiler plate or determine the order of which providers to create first.

package main 

import "example"

func main() {
    component := example.GetExampleComponent()
    fmt.Printf(component.Address())
}

Troubleshooting Errors

Features

di checks the correctness of your provider files and alerts of the following errors

• providers which circularly depend on each other or themselves
• providers which have missing/undefined dependencies