What is modularity in the context of application development?

Modular architecture is an approach where an application is divided into small, independent modules. Each module is responsible for a specific functionality or layer of the application.

Advantages of modular architecture:

• Improved code organization: Logically related parts of the application are grouped into separate modules, making navigation and understanding of the project structure easier.
• Faster build times: Changes in one module require recompiling only that module and its dependencies, not the entire project.
• Increased reusability: Modules containing common functionality (e.g., UI components, utilities) can be easily used in different parts of the application or even in other projects.
• Easier testing: Each module can be tested independently, simplifying the writing and maintenance of tests.
• Better scalability: The team can work on different modules in parallel, reducing the risk of conflicts.
• Dependency isolation: Modules have explicit dependencies on each other, making the application's structure transparent and reducing the risk of unforeseen changes.

Examples of module types in an Android application:

• app (main application module)
• feature-login (login functionality module)
• feature-profile (user profile module)
• data (data handling module)
• domain (business logic module)
• common-ui (module with common UI components)
• utils (utility module)

Modules are usually linked through dependencies declared in build.gradle files:

// build.gradle (Module: app)
dependencies {
    // Dependency of the root module on other modules
    implementation project(':feature-login')
    implementation project(':feature-profile')
    implementation project(':data')
}

// build.gradle (Module: feature-login)
dependencies {
    // Dependency of the feature module on data and utility modules
    implementation project(':data')
    implementation project(':utils')
}