Using danceable/container for Dependency Injection | DI (dependency injection) in Go

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Using danceable/container for Dependency Injection | DI (dependency injection) in Go

The two previous parts covered the concepts; this one is hands-on. Install danceable/container, bind and resolve services, control their lifetime with bind.Singleton() and bind.Lazy(), and let the container call your functions — then organize the whole thing with danceable/provider's Register / Boot / Terminate lifecycle.

In this part we introduce danceable/container and danceable/provider for dependency management and service lifecycle management, and then use them to build a multilingual blog.

Using `danceable/container` as a service container in Go

In the previous part we covered the service container concept. Here we get to know danceable/container and learn how to use it.

Installing the package:

go get github.com/danceable/container

To create a container, use the New method:

package main

import "github.com/danceable/container"

func main() {
    c := container.New()
}

With the Bind method we tell the container how to create a service:

package main

import (
    "github.com/danceable/container"
    "go.mongodb.org/mongo-driver/v2/mongo"
)

func main() {
    c := container.New()
    
    // bind to container
    c.Bind(func()  (*mongo.Client, error) {
        uri := "mongodb://test_username:test_passwrod@mongodb:27317"
    
        return mongo.Connect(options.Client().ApplyURI(uri))
    })
}

With the Resolve method we ask the container to hand us a MongoDB connection:

package main

import (
    "github.com/danceable/container"
    
    "go.mongodb.org/mongo-driver/v2/mongo"
    "go.mongodb.org/mongo-driver/v2/mongo/options"
    "go.mongodb.org/mongo-driver/v2/mongo/readpref"
)

func main() {
    c := container.New()
    
    // bind to container
    c.Bind(func()  (*mongo.Client, error) {
        uri := "mongodb://test_username:test_passwrod@mongodb:27017"
    
        return mongo.Connect(options.Client().ApplyURI(uri))
    })
    
    // resolve from container
    var client *mongo.Client
    if err := c.Resolve(&client); err != nil {
        log.Fatal(err)
    }
    
    ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
    defer cancel()
    
    // ping the DB
    client.Ping(ctx, readpref.Primary())
}

Every time we call Resolve, the function we registered with the container is invoked, a value of that type is created, and it's placed into our variable. If the last value the function returns is an error, Resolve returns that error.

Sharing a single instance of a service (singleton)

Sometimes we need only one instance of a service to exist. In that case we can pass bind.Singleton() to the Bind method:

package main

import (
    "github.com/danceable/container"
    "github.com/danceable/container/bind"
    
    "go.mongodb.org/mongo-driver/v2/mongo"
    "go.mongodb.org/mongo-driver/v2/mongo/options"
    "go.mongodb.org/mongo-driver/v2/mongo/readpref"
)

func main() {
    c := container.New()
    
    // bind to container
    c.Bind(func()  (*mongo.Client, error) {
        uri := "mongodb://test_username:test_passwrod@mongodb:27017"
    
        return mongo.Connect(options.Client().ApplyURI(uri))
    }, bind.Singleton())
    
    // resolve from container
    var client *mongo.Client
    if err := c.Resolve(&client); err != nil {
        log.Fatal(err)
    }
    
    ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
    defer cancel()
    
    // ping the DB
    client.Ping(ctx, readpref.Primary())
}

#golang #go

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