The Pragmatic Programmer - Chapter 5: Bend or Break

Decoupling

• Decoupled code is easy to change (ETC).
• Tell, don’t ask.
• Don’t chain method calls.
• Avoid global data.
• If it’s important enough to be global, wrap it in an API.

Juggling The Real World

• Try to use finite state machine to handle events.
• Observer Pattern:
  • Push functions reference onto a list and then call those functions when the event occurs.
  • Problems:
    • Coupling
    • Callbacks are handled inline synchronously -> Performance bottleneck
• Publish/Subscribe (Pub/Sub) Pattern:
  • Potentially asynchronous
  • Solve coupling and performance problem
• Reactive programming, stream and events:
  • A reacts as B changes.
  • Event streams unify sync and async processing behind a common and conveniente API.

Transforming Programming

• Programming is about code, but programs are about data.
• Think about data transformation.
• Don’t hoard state; Pass it around.
• We never pass raw values between transformations. Instead, we wrap them in a data structure.

Inheritance Tax

• Inheritance is coupling.
• Don’t pay inheritance tax.
• Alternatives:
  • Interfaces and protocols
  • Delegation
  • Mixins and traits
• Prefer interfaces to express polymorphism.
• Use mixins to share functionality.

Configuration

• Parameterize your application using external config.
• Wrap configuration behind a thin API.
• Code that don’t adapt, die.