Inject: Compile-time DI initialization in Go

Inject is a compile-time dependency-injection library. Supported injection types are:

• Singleton - single instance for the entire application;
• Transient - each time a new instance is created.

The library verifies injection consistency (transient instances cannot be injected into singletons because transient will become singleton).

Installing

1. Install the CLI for code generation

go get github.com/MyNihongo/inject/cmd/inject

2. Add the library itself

go get github.com/MyNihongo/inject

Ensure that $GOPATH/bin is added to your $PATH.

Define a service collection

1. Create a new file with the name serviceCollection.go. Inject will look for a file with this name;
2. In the file define a function BuildServiceProvider. Inject will look for a function with this name. In this function all services should be declared.
3. Add //go:generate inject to the header of the file.
4. Run go generate .\...

//go:generate inject
package examples

import (
	"github.com/MyNihongo/inject"
	"github.com/MyNihongo/inject/examples/pkg1"
	"github.com/MyNihongo/inject/examples/pkg2"
	"github.com/MyNihongo/inject/examples/pkg3"
)

func BuildServiceProvider() {
	inject.NewServiceCollection().
		AddSingleton(pkg1.GetService1).
		AddTransient(pkg2.GetService2).
		AddTransient(pkg2.GetInnerService).
		AddTransient(pkg3.GetService3)
}

This will generate the following code in the file serviceProvider_gen.go.

// Code generated by my-nihongo-di. DO NOT EDIT.
package examples

import (
	pkg1 "github.com/MyNihongo/inject/examples/pkg1"
	pkg2 "github.com/MyNihongo/inject/examples/pkg2"
	pkg3 "github.com/MyNihongo/inject/examples/pkg3"
	"sync"
)

var impl_Service1 pkg1.Service1

// ProvideService1 provides a singleton instance of github.com/MyNihongo/inject/examples/pkg1.Service1
func ProvideService1() pkg1.Service1 {
	sync.DoOnce(func() {
		impl_Service1 = pkg1.GetService1()
	})
	return impl_Service1
}

// ProvideInnerService provides a transient instance of github.com/MyNihongo/inject/examples/pkg2.InnerService
func ProvideInnerService() pkg2.InnerService {
	return pkg2.GetInnerService()
}

// ProvideService2 provides a transient instance of github.com/MyNihongo/inject/examples/pkg2.Service2
func ProvideService2() pkg2.Service2 {
	p0 := ProvideInnerService()
	p1 := ProvideService3()
	return pkg2.GetService2(p0, p1)
}

// ProvideService3 provides a transient instance of github.com/MyNihongo/inject/examples/pkg3.Service3
func ProvideService3() pkg3.Service3 {
	return pkg3.GetService3()
}