[閱讀筆記] Clean Code — Chapter 12 Emergence

Getting Clean via Emergence Design

• Runs all the tests
• Contains no duplication
• Expresses the intent of the programmer
• Minimizes the number of classes and methods

Simple Design Rule 1: Runs All the Tests

• A system that is comprehensively tested and passes all of its tests all of the time is a testable system.
• A system that cannot be verified should never be deployed

Simple Design Rule 2: No Duplication

• Duplication is the primary enemy of a well-designed system
• Duplication: Lines of code that look exactly alike are
• TEMPLATE METHOD

public void accrueVacation() {
      calculateBaseVacationHours();
      alterForLegalMinimums();
      applyToPayroll();
}
private void calculateBaseVacationHours() { /* ... */ };
abstract protected void alterForLegalMinimums();
private void applyToPayroll() { /* ... */ };

Simple Design Rule 3: Expressive

• Code should clearly express the intent of its author
• How to:
  1. Choosing good names
  2. Keeping your functions and classes small
  3. Using standard nomenclature (ex. standard pattern names)
  4. Well-written unit tests

Simple Design Rule 4: Minimal Classes and Methods

• Take rule 1–3 too far → too many tiny classes and methods
• Overall system small while we are also keeping our functions and classes small