Dependency Injection design pattern (DI)

Mariusz Postol

I did ask GPT: Please give me a code snippet of dependency injection in C#.

Ref: OpenAI. (2024). ChatGPT (3.5) [Large language model].

I have got the following answer:

Certainly, here's a simple example of dependency injection in C# using constructor injection:

```csharp
using System;

// Interface for the service
public interface IService
{
    void PerformAction();
}

// Implementation of the service
public class Service : IService
{
    public void PerformAction()
    {
        Console.WriteLine("Action performed by the service.");
    }
}

// Class that depends on the service through constructor injection
public class Client
{
    private readonly IService _service;

    // Constructor with IService parameter for dependency injection
    public Client(IService service)
    {
        _service = service;
    }

    public void DoWork()
    {
        // Using the injected service
        _service.PerformAction();
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Creating an instance of the service
        IService service = new Service();

        // Creating an instance of the client and injecting the service
        Client client = new Client(service);

        // Using the client
        client.DoWork();
    }
}
```

In this example, `Client` class depends on `IService`, and the dependency is injected through its constructor. The `Main` method demonstrates how you can create instances of the service and client and inject the service into the client.

The similar answer we can get from many sources. Here we have methods invocation (constructor), object instantiation, Passing parameters, abstraction (interface), and inheritance (Service inherits interface). From other sources, I know that DI is a design pattern. We use patterns to solve a problem.

What is the problem in this case?

Why do we need a special term to name something we are familiar with?

4 Replies

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Mariusz Postol2y ago
In the article titled Programming in Practice Discipline, I have embedded a detailed description in the chapter "Dependency Injection (DI)". Check it out and let me know what you think about this approach. Dependency Injection is presented as a design pattern that can be applied to solve an issue to replace a concrete type with an abstract one in case the concrete type is invisible.
0
Tuhin Paul2y ago
While the code snippet you provided demonstrates the mechanics of DI, it's essential to understand the problems it addresses and why it's valuable:
1. Traditional object creation often involves classes directly instantiating their dependencies within themselves. This creates tight coupling, making code harder to change, test, and reuse.

2. Classes often become burdened with the responsibility of creating and managing their dependencies, leading to, scattered creation logic, making it difficult to track and maintain how objects are created.
-1

Mariusz Postol2y ago

I believe that DI is a design pattern, and we are talking about real programming in practice problems. It is not only a question related to terminology. The same result we can obtain by removing abstraction and inheritance.

using System;

// Implementation of the service
public class Service
{
    public void PerformAction()
    {
        Console.WriteLine("Action performed by the service.");
    }
}

// Class that depends on the service through constructor injection
public class Client
{
    private readonly Service _service;

    // Constructor with IService parameter for dependency injection
    public Client(Service service)
    {
        _service = service;
    }

    public void DoWork()
    {
        // Using the injected service
        _service.PerformAction();
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Creating an instance of the service
        IService service = new Service();

        // Creating an instance of the client and injecting the service
        Client client = new Client(service);

        // Using the client
        client.DoWork();
    }
}

The question is about a simple condition that a software developer can use to obtain a yes/no answer to the question do I have the problem (reason) appropriate to apply dependency injection (use abstraction and inheritance)? Any answers like to improve flexibility, to be open for future implementation don't have answers yes/no. Today it could be no (I don't need flexibility), tomorrow it could be yes (yes flexibility is vital).

Sam Hobbs2y ago
People constantly make up new terms to refer to old things. People say blog and blog post to refer to things that just a few years ago were called articles. People use the word face instead of more approriate words, such as have. People say achieve instead of do.

Microsoft constantly makes up confusing terms, such as Visual Studio and Visual Studio Code.

A really big problem is that when someone says anythihng about terminology, people get upset. People ask programming questions and other people try to help them do things the correct way but anytime someone says something about grammar they are considered innaprppriate.
+3