Modular programming

My notes on modular programming

“And you can easily swap blocks. Want a new camera in the app? Change the camera framework, API remains more or less the same”


  • Modular: single ‘responsibility’
  • monolith: tightly coupled
  • abstract systems into manageable layers

Benefits of modular programming:

  • Speed of implementing new stuff,
  • Modularity and easily change components of the app,
  • Scalability of the team, easier to find it’s way around, make programmers happy
  • Modules are reusable across projects
  • Each one have a independent test app, tests (and repo of course)
  • Carthage, new functionality goes into a framework. For instance if you make a new password strength checker -> own framework
  • Keeping time-saving-extensions in classes makes them prone to becoming out of sync with other parts of the code
  • Many modern apps often have 20-40 internal .framework dependencies
  • Divided project into logical parts that are living their life.
  • Developers can run and develop only specific parts of the app (specific framework) without compiling everything.
  • More flexibility on the project. A framework can be quite easily taken out or linked back into the project.
  • Develop more efficiently using XCPlaygrounds as a project cannot be imported to the XCPlaygrounds but a framework can. A perfect use case is for developing UIComponents. With Playgrounds there is almost an instant build of the view.
  • Every framework contains its unit tests so it can be run in isolation from the rest of the app.
  • Developers can work more async, isolated on their own tasks without disturbing progress of the main project
  • Modules can live isolated while other modules move on by using legacy versions of dependencies
  • Access control (limit with the internal accessor, only make public methods that can be accessed from outside)
  • Shorter more explicit naming of classes: Not RemoteImageAccessManipulator but rather just internal AccessManipulator in a RemoteImage module

Nails monolith vs modular:

Additional reading:

Between 200-400 lines max:

In nonmathematical terms, Hatton’s empirical results imply a sweet spot between 200 and 400 logical lines of code that minimizes probable defect density, all other factors (such as programmer skill) being equal. This size is independent of the language being used — an observation which strongly reinforces the advice given elsewhere in this book to program with the most powerful languages and tools you can. Beware of taking these numbers too literally however. Methods for counting lines of code vary considerably according to what the analyst considers a logical line, and other biases (such as whether comments are stripped). Hatton himself suggests as a rule of thumb a 2x conversion between logical and physical lines, suggesting an optimal range of 400–800 physical lines. Ref: