Inappropriate Intimacy

Classes that know too much about each other’s internals.

“Sometimes classes become far too intimate and spend too much time delving in each others’ private parts.” – Fowler & Beck

Signs of Use (Symptoms)

  • One class accesses another’s private fields (perhaps via reflection or friend access).
  • Bidirectional dependencies.

Why it is bad (Consequences)

  • Fragility: Change one class, break the other.
  • Encapsulation broken: Internals are exposed.

Why it happens (Root Cause)

Classes were developed together and shortcuts were taken.

When it might be okay (Exceptions)

  • Helper/Factory classes tightly aligned with the target.

Explanation

Problem

User knows internal details of Session. Session knows internal details of User.

The Flaw

No clear boundaries. Changes ripple.

Real world analogy

Two roommates who share everything, including toothbrushes. Boundaries matter.

Refactoring Solution

  • Move Method / Move Field: Reduce dependencies.
  • Extract Class: Create intermediary.
  • Hide Delegate.

Pros and Cons (of the Antipattern)

Pros (Why people do it) Cons (The price you pay)
  • Quick access
    		•
  • Tight coupling
    		•

    Comparison

    • Related Antipatterns: Feature Envy.
    • Related Principles: Low Coupling, Encapsulation.

    Code example

    Typescript

    Bad (The Antipattern)

    Good (The Fix)