Use a utility layer to provide reusable functions or classes

Oct 13, 2025 by wbrum.org 122 views

Introduction

When designing a software application using the Onion or Clean Architecture pattern, it's essential to consider the placement of utility classes or functions that don't directly interact with the business logic. In this article, we'll explore the best practices for placing an Excel/PDF generator class or function in an Onion/Clean Architecture.

What is Onion/Clean Architecture?

Onion Architecture and Clean Architecture are software design patterns that aim to separate the application's business logic from its infrastructure and presentation layers. The Onion Architecture is a variation of the Clean Architecture pattern, which was first introduced by Robert C. Martin (Uncle Bob). Both patterns emphasize the importance of separating the application's core logic from its external dependencies.

Onion Architecture

In the Onion Architecture, the application's core logic is represented by the innermost layers, which include the business logic and the domain model. The outer layers represent the infrastructure and presentation layers.

Clean Architecture

In the Clean Architecture, the application's core logic is represented by the entities and use cases, which are decoupled from the infrastructure and presentation layers.

Where to put the Excel/PDF generator class or function?

When deciding where to place the Excel/PDF generator class or function, we need to consider the following factors:

Dependency: Does the Excel/PDF generator class or function depend on any external libraries or frameworks that are not part of the application's core logic?
Reusability: Is the Excel/PDF generator class or function reusable across multiple applications or projects?
Complexity: Does the Excel/PDF generator class or function introduce complexity to the application's core logic?

Option 1: Infrastructure Layer

One possible location for the Excel/PDF generator class or function is the infrastructure layer. This layer is responsible for interacting with external systems, such as databases, file systems, and third-party services.

Pros:

The Excel/PDF generator class or function is decoupled from the application's core logic.
The infrastructure layer is responsible for handling external dependencies.

Cons:

The Excel/PDF generator class or function may introduce complexity to the infrastructure layer.
The infrastructure layer may become bloated with utility classes or functions.

Option 2: Application Layer

Another possible location for the Excel/PDF generator class or function is the application layer. This layer is responsible for coordinating the interactions between the business logic and the infrastructure layer.

Pros:

The Excel/PDF generator class or function is still decoupled from the business logic.
The application layer is responsible for handling complex business logic.

Cons:

The Excel/PDF generator class or function may introduce complexity to the application layer.
The application layer may become bloated with utility classes or functions.

Option 3: Utility Layer

A third possible location for the Excel/PDF generator class or function is the utility layer. This layer is responsible for providing reusable functions or classes that can be used across multiple applications or projects.

Pros:

The Excel/PDF generator class or function is decoupled from the application's core logic.
The utility layer is responsible for providing reusable functions or classes.

Cons:

The Excel/PDF generator class or function may not be tightly coupled with the application's core logic.
The utility layer may become bloated with utility classes or functions.

Conclusion

In conclusion, the placement of the Excel/PDF generator class or function in an Onion/Clean Architecture depends on the specific requirements of the application. If the Excel/PDF generator class or function is tightly coupled with the application's core logic, it's best to place it in the infrastructure layer. If the Excel/PDF generator class or function is reusable across multiple applications or projects, it's best to place it in the utility layer.

Best Practices

When designing an Onion/Clean Architecture, follow these best practices:

Separate the application's core logic from its infrastructure and presentation layers.
Use a utility layer to provide reusable functions or classes.
Avoid introducing complexity to the application's core logic.
Use dependency injection to decouple the application's components.

Example Code

Here's an example of how to implement the Excel/PDF generator class or function in a .NET Core 6 application using the Onion Architecture pattern:

// Infrastructure Layer
public interface IExcelGenerator
{
    void GenerateExcelReport();
}
public class ExcelGenerator : IExcelGenerator
{
public void GenerateExcelReport()
{
// Generate Excel report using EPPlus library
}
}
// Application Layer
public interface IReportService
{
void GenerateReport();
}
public class ReportService : IReportService
{
private readonly IExcelGenerator _excelGenerator;
public ReportService(IExcelGenerator excelGenerator)
{
    _excelGenerator = excelGenerator;
}

public void GenerateReport()
{
    _excelGenerator.GenerateExcelReport();
}

}
// Utility Layer
public static class ReportHelper
{
public static void GeneratePdfReport()
{
// Generate PDF report using iTextSharp library
}
}

In this example, the Excel/PDF generator class or function is placed in the infrastructure layer, and the application layer uses dependency injection to decouple the Excel/PDF generator class or function from the business logic. The utility layer provides a reusable function for generating PDF reports.

Introduction

In our previous article, we explored the best practices for placing an Excel/PDF generator class or function in an Onion/Clean Architecture. In this article, we'll answer some frequently asked questions (FAQs) related to the placement of the Excel/PDF generator class or function.

Q&A

Q1: What is the difference between Onion Architecture and Clean Architecture?

A1: Onion Architecture and Clean Architecture are software design patterns that aim to separate the application's business logic from its infrastructure and presentation layers. The main difference between the two patterns is that Onion Architecture is a variation of Clean Architecture, which was first introduced by Robert C. Martin (Uncle Bob).

Q2: Where should I place the Excel/PDF generator class or function in a .NET Core 6 application?

A2: The placement of the Excel/PDF generator class or function in a .NET Core 6 application depends on the specific requirements of the application. If the Excel/PDF generator class or function is tightly coupled with the application's core logic, it's best to place it in the infrastructure layer. If the Excel/PDF generator class or function is reusable across multiple applications or projects, it's best to place it in the utility layer.

Q3: What is the utility layer in Onion/Clean Architecture?

A3: The utility layer in Onion/Clean Architecture is responsible for providing reusable functions or classes that can be used across multiple applications or projects. The utility layer is typically used to provide utility functions or classes that are not part of the application's core logic.

Q4: How do I avoid introducing complexity to the application's core logic?

A4: To avoid introducing complexity to the application's core logic, you should separate the application's core logic from its infrastructure and presentation layers. You should also use dependency injection to decouple the application's components and avoid tightly coupling the Excel/PDF generator class or function with the application's core logic.

Q5: What is the difference between dependency injection and tightly coupling?

A5: Dependency injection is a design pattern that allows you to decouple the application's components by providing the dependencies required by the components. Tightly coupling, on the other hand, is a design pattern that tightly couples the components by making them dependent on each other.

Q6: How do I use dependency injection to decouple the Excel/PDF generator class or function?

A6: To use dependency injection to decouple the Excel/PDF generator class or function, you should create an interface for the Excel/PDF generator class or function and inject the interface into the application's components. You should then use the interface to decouple the Excel/PDF generator class or function from the application's core logic.

Q7: What is the best practice for naming the Excel/PDF generator class or function?

A7: The best practice for naming the Excel/PDF generator class or function is to use a descriptive name that indicates the purpose of the class or function. For example, you could name the Excel/PDF generator class or function "ExcelGenerator" or "PdfGenerator".

Q8: How do I test the Excel/PDF generator class or function?

A8: To test the Excel/PDF generator class or function, you should create unit tests that verify the correctness of the class or function. You should also use mocking to isolate the dependencies required by the class or function.

Q9: What is the difference between unit testing and integration testing?

A9: Unit testing is a type of testing that verifies the correctness of individual units of code, such as methods or classes. Integration testing, on the other hand, is a type of testing that verifies the correctness of the interactions between multiple units of code.

Q10: How do I use mocking to isolate the dependencies required by the Excel/PDF generator class or function?

A10: To use mocking to isolate the dependencies required by the Excel/PDF generator class or function, you should create mock objects that mimic the behavior of the dependencies. You should then use the mock objects to isolate the dependencies required by the class or function.

Conclusion

In conclusion, the placement of the Excel/PDF generator class or function in an Onion/Clean Architecture depends on the specific requirements of the application. By following the best practices outlined in this article, you can ensure that your application is designed with maintainability, scalability, and testability in mind.

Best Practices

When designing an Onion/Clean Architecture, follow these best practices:

Separate the application's core logic from its infrastructure and presentation layers.
Use a utility layer to provide reusable functions or classes.
Avoid introducing complexity to the application's core logic.
Use dependency injection to decouple the application's components.
Use mocking to isolate the dependencies required by the application's components.
Test the application's components thoroughly using unit tests and integration tests.

Example Code

Here's an example of how to implement the Excel/PDF generator class or function in a .NET Core 6 application using the Onion Architecture pattern:

// Infrastructure Layer
public interface IExcelGenerator
{
    void GenerateExcelReport();
}
public class ExcelGenerator : IExcelGenerator
{
public void GenerateExcelReport()
{
// Generate Excel report using EPPlus library
}
}
// Application Layer
public interface IReportService
{
void GenerateReport();
}
public class ReportService : IReportService
{
private readonly IExcelGenerator _excelGenerator;
public ReportService(IExcelGenerator excelGenerator)
{
    _excelGenerator = excelGenerator;
}

public void GenerateReport()
{
    _excelGenerator.GenerateExcelReport();
}

}
// Utility Layer
public static class ReportHelper
{
public static void GeneratePdfReport()
{
// Generate PDF report using iTextSharp library
}
}