Обзор “Clean Architecture” (Часть I: дизайн и архитектура, парадигмы программирования)

Рис. 1 “Обложки книг на русском и английском”
Рис. 2 “Содержание книги”

Introduction

When software is done right, it requires a fraction of the human resources to create and maintain. Changes are simple and rapid. Defects are few and far between. Effort is minimized, and functionality and flexibility are maximized.

One of the goals of this book is to cut through all that confusion and to define, once and for all, what design and architecture are. For starters, I’ll assert that there is no difference between them. None at all.

Рис. 3 “Взаимоотношение между архитектурой и дизайном”

The only way to go fast, is to go well

To build a system with a design and an architecture that minimize effort and maximize productivity, you need to know which attributes of system architecture lead to that end.

That’s what this book is about. It describes what good clean architectures and designs look like, so that software developers can build systems that will have long profitable lifetimes.

Рис.4 “Values of software system”
Рис.5 “Матрица Эйзенхауэра в применении к решениям вида behavior и architecture”

The dilemma for software developers is that business managers are not equipped to evaluate the importance of architecture. That’s what software developers were hired to do. Therefore it is the responsibility of the software development team to assert the importance of architecture over the urgency of features.

If architecture comes last, then the system will become ever more costly to develop, and eventually change will become practically impossible for part or all of the system.

Starting with the bricks: programming paradigms

Рис.6 “Обзор парадигм программирования”
Рис.7 “Структуры, из которых можно сконструировать любую программу”
Рис.8 “Базовый элемент SADT и его декомпозиция”

The nature of scientific theories and laws: They are falsifiable but not provable.

Testing shows the presence, not the absence, of bugs

Structured programming forces us to recursively decompose a program into a set of small provable functions. We can then use tests to try to prove those small provable functions incorrect.

Рис.9 “Что такое объектно-ориентированное программирование”

What is OO? There are many opinions and many answers to this question. To the software architect, however, the answer is clear: OO is the ability, through the use of polymorphism, to gain absolute control over every source code dependency in the system. It allows the architect to create a plugin architecture, in which modules that contain high-level policies are independent of modules that contain low-level details. The low-level details are relegated to plugin modules that can be deployed and developed independently from the modules that contain high-level policies.

The answer is absurdly simple: All race conditions, deadlock conditions, and concurrent update problems are due to mutable variables. You cannot have a race condition or a concurrent update problem if no variable is ever updated. You cannot have deadlocks without mutable locks.

The immutable components perform their tasks in a purely functional way, without using any mutable variables. The immutable components communicate with one or more other components that are not purely functional, and allow for the state of variables to be mutated

Transactional memory simply treats variables in memory the same way a database treats records on disk. It protects those variables with a transaction- or retry-based scheme.

Event sourcing is a strategy wherein we store the transactions, but not the state. When state is required, we simply apply all the transactions from the beginning of time.

Software — the stuff of computer programs — is composed of sequence, selection, iteration, and indirection. Nothing more. Nothing less.

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Director of digital ecosystem development department at Tinkoff. Bachelor at applied math, Master at system analysis, Postgraduate studies at economics.

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