Lewis - Clean Architecture

Copyright 2020 by Elijah Lewis - All rights reserved.

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TABLE OF CONTENTS

A Comprehensive Beginner's Guide to Learn
the Realms of Clean Architecture from A-Z

Best Tips and Tricks to Learn and use
Clean Architecture Theories to the Best

Advanced and Effective Strategies
Using Clean Architecture Principles

ELIJAH LEWIS

Success in software development requires architecture as much as a building project, for example. Software architecture proposes better organization, quality in performance, reliability, system portability, impacting non-functional requirements directly.

The Layered Architecture

Layered architecture came up with the idea of separating presentation from business logic from the software. This way of organizing software development is to split the application into layers to separate responsibilities and make the software easier to maintain and reuse.

For the architecture of small software, usually, three layers are listed:

• UI (User Interface) - UI layer makes interaction and presentation of data to the user;
• Business Logic Layer (BLL) - Business Layer stores logic, dealing with software business rules, also called business logic layer or domain layer.
• DAL (Data Access Layer) - Data Access Layer: responsible for accessing and persisting application data;

The operation of this architecture provides the following operation, and the interface layer should contain the pages to interact with the user obtaining information from the business layer, which in turn handles the application business rules and obtains information from the data access layer. The interface layer cannot know anything about the data access layer.

The purpose of this architecture is to create the possibility to change or update one layer without interfering with the other layer, based on a level of abstraction between the layers.

Looking at the diagram on the left, it is clear that the order of the three layers mentioned imposes a dependence of the upper layer to the lower one. Which can generate a possible problem in this form of traditional architecture? Designed in this order, software developers may have difficulty when making any changes to the System Database. They may make it difficult to test business logic code because it depends on the data access layer.

There are currently many architectures that rely on layered architecture, some increasing the number of layers, replacing or reversing the order of certain layers to bring more benefits to meeting non-functional requirements. Amid layered architecture, and the need for software changes came to The Clean Architecture.

The Clean Architecture

The clean architecture created by Uncle Bob (Robert C. Martin), represented by a diagram with concentric circular layers, is based on the isolation of these layers, so that replacement of components in the layer is easy and does not affect the entire system.

Swapping one component for another should not make the software work differently, or even stop working. Layer responsibilities are defined as follows:

Framework and Drivers

It is the outermost layer, protects the system from changes in detail, i.e., changes in this layer do not imply software functionality, so it is the detail layer and communicates with the next inner circle.

Interfaces Adapters (Adapters Interface)

Converts user-entered data into a structure that interacts with the system, where the presenters, controls, gateways, and repositories reside.

Application Business Rules (Application Business Rules )

It is responsible for processing information, where use cases are, where business rules are validated, and feedback on what is happening.

Corporate Business Rules (Enterprise Business Rules)

The layer of entities where business-level business rule codes are. These codes must be ready for reuse.

In the Clean Architecture proposal, all dependencies must point inwards; the outer circles are mechanisms and inner politics. In other words, the source code should not be aware of the layers external to your layer, should not have any dependency on these so the name of Dependency Rule.

The whole division and concept of this architecture provide a better organization of the software structure, making it easier for possible changes, due to the isolation of the layers. At any time, the interface components may be modified and in no way affect the meaning and operation of the software.

Are you interested in software architecture? I hope so because this is one of those aspects that should interest you regardless of your level of experience in the world of software development. If you are a junior programmer, you should be interested in it as soon as possible if you want to evolve as a professional.