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Key Concepts & Challenges

1. Boundary Definition

   • Purpose: Isolate components to manage change and reduce coupling.
   • Mechanisms: Use interfaces, dependency inversion, or abstract classes to decouple high-level policies from low-level details.

2. Dependency Direction

   • Rule: Dependencies should point toward stable abstractions (e.g., interfaces) to invert control.

3. Plugin Architecture

   • Goal: Allow dynamic extension by isolating core logic from plugins.

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Code Examples with Tests

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Example 1: Interface-Based Boundary (C++)

Scenario: Separate data processing from I/O operations.
Boundary: Define an IWriter interface to abstract output mechanisms.

// File: iwriter.h
#pragma once
#include <string>class IWriter {
public:virtual ~IWriter() = default;virtual void write(const std::string& data) = 0;
};// File: console_writer.h
#include "iwriter.h"
class ConsoleWriter : public IWriter {
public:void write(const std::string& data) override {std::cout << "[CONSOLE] " << data << std::endl;}
};// File: data_processor.cpp
#include "iwriter.h"
class DataProcessor {IWriter* writer;
public:DataProcessor(IWriter* w) : writer(w) {}void process() {writer->write("Processing complete.");}
};// Test in main.cpp
#include "console_writer.h"
int main() {ConsoleWriter cw;DataProcessor dp(&cw);dp.process();  // Output: [CONSOLE] Processing complete.return 0;
}

Compilation:

g++ -std=c++17 main.cpp console_writer.cpp data_processor.cpp -o app && ./app

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Example 2: Dependency Inversion ©

Scenario: Decouple a Logger from its output method.
Boundary: Use function pointers to invert dependencies.

// File: logger.h
#pragma once
typedef void (